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227 terms


coined by Ernest Haeckle in 1866; a scientific study of the relationship between organisms and their environment; a body of knowledge considering the economy of nature; "study of the house"; energy is the currency of nature
Definitions of Ecology over time
• Haeckel's definition (1869) - "Ecology is the body of knowledge concerning the economy of nature - the investigation of the total relations of the animal (organism) to both its organic and inorganic environment".
• Odum (1971) - "the study of the structure and function of
• Pianka (1988) - "the study of the relationships between
organisms and the totality of the physical and biological factors affecting them or influenced by them".
Definitions of Ecology over time
• Dodson (1998) - "the study of the relationships, distribution,
and abundance of organisms, or groups of organisms, in an
• Krebs (2009) - "the scientific study of the interactions that
determine the distribution and abundance of organisms".
• Smith and Smith (2012) - "the study of the relationships
between organisms and their environment".
Ecology isn't
Environmental Science
Resource management
But we would like to apply ecological principles to understand the underlying processes in order to manage these resources for perpetuity
physical and chemical conditions as well as biological components of an organisms surroundings and the array of organisms that exist within its confines (interactions with the physical world, same species and other species); abiotic + biotic = environment; factors which surround and potentially influence an organism
Physical and Chemical Conditions
all influence basic physiologival processes crucial to survival (growth and development); required to pass genes on to the next generation, struggle for existence (ex. ambient temperature, moisture, CO2 concentration, light intensity)
Physical and chemical conditions influence an
organism's physiology
- Temperature
- Light
- Oxygen
- Carbon dioxide
Biotic and Abiotic
Biotic: living
Abiotic: non-living (physical and chemical components)
Organisms interact with their environment in the context of the ecosystem. A system formed by the interaction of a community of organisms with their living and physical environment (biotic and abiotic), function as related parts that form a unit. Community + physcial environment = ecosystem
ecological systems can be viewed in a hierarchical framework; each have unique patterns and processes; requires different questions and study approaches for each element
a single organism; basic unit of ecology; an individual responds to an environment; interactions among individuals of the same or different species define communities individuals pass genes on to the next generation; collective birth and death of individuals defines the dynamic of the population
group of individuals of the same species that occupy a given area; can interact (compete over shared resources, predation,mutual benefit) with the same species as well as other species
group of populations that exploit the same class of resource in a similar way (obtain their food from the same prey in the same way)
all populations of different species living and interacting within an ecosystem;how inclusive a community is depends on
the particular ecologists frame (scale) of reference; community + physical environment (abiotic) = ecosystem
area of land or water composed of a patchwork of communities and ecosystems, linked by the dispersal of organisms and the exchange of materials
broad-scale regions dominated by similar types of ecosystems, geographic regions that have similar geological and climatic conditions that support similar types of communities and ecosystems
thin layer about the Earth that supports all life; encapsulates all ecological systems
Landscape & Ecosystem & Community
linked through such processes as the dispersal of organisms and exchange of materials and ecosystems
activism with the stated aim of protecting the natural environment, particularly from human activities
Scientific Method
All ecological studies begin with observation; questions emerge; hypothesis developed (proposed answer to question, must be testable through observation and experiments)
developed from research date, allow us to predict behaviour or response using a set of explicit assumptions; are abstract simplified representations of natural phenomena,have assumptions that allow us to predict behavior or response,
can be mathematical, verbal, or pictorial
science is always uncertain; arises from limitation that we can only focus on a small subset in nature; results in incomlete perspective; goal of hypothesis is to eliminate incorrect ideas
"study of the household"
economics of ecology; how we manage our household (the planet); generation and consumption of resources, became important in the lat 1950's; not managing resources the way we should be; energy is the currency of ecology; how much energy transferred = how much service can be done
Environmental Science
the study of the human effect on natural systems
Study Ecology
to understand the principles of operation of natural systems and predict their response to change; mimic the natural processes in order to achieve longterm resource management; understand how the world works (we are shaped by our surroundings, natural processes and patterns); minimize the detrimental affects of our actions on the environment
Study Ecology
ecological systems are models for sustainability; manage conditions to support present day life; resources are limited;understand the laws of nature that impose the limitations on the interactions between organisms and their environments
Fundamental Principles of Ecology
1. Organisms/Environmental Conditions/Resources are distributed in space and time in a heterogeneous manner.
2. Organisms interact with their biotic and abiotic environment.
3.Distributions of organsisms depend on their circumstances.
Fundamental Principles of Ecology
4. Resources are finite and distributed in space and time in a heterogeneous manner.
5. All organisms are mortal.
6. All ecological properties of species are a result of evolution.
the spatial property of being scattered about over an area or volume
Spatial distribution
physical location of geographic phenomena across space, where they are throughout the landscape
Temporal distribution
how many over time
Total number of organisms in a biological community
randomized, clustered, can't see a pattern, not mixed across a whole landscape evenly, no guarantee that biotic/abiotic material will be found there (fertile & infertile soil conditions vary)
Processes regulating the distrubution & abundance of organisms
Environment (physical, chemical, and biological factors) and Relationships (interactions with environment and other organisms)
Abiotic environment
Made up of:
1) physical factors such as solar radiation, temperature,
moisture, wind, etc.
2) chemical factors such as nutrients, pH toxic elements,
Biotic environment
Include factors such as competition, herbivory, predation, mutualism, etc.
immediate small-scale environment of an organism or a part of an organism; distinguished from its immediate surroundings by such factors as the amount of incident light, the degree of moisture, and the range of temperatures.;
large-scale and long-term environment and conditions that affect an organism.
Ecology as an interdisciplinary science
interactions with organisms and the environment involves physiological, behavioural and physical responses; draws upon fields of physiology, biochemistry, genetics, geology, hydrology, and meteorolgy
An environment in which organisms carry out
their "struggle for existence";includes an environment's
physical conditions and the array of organisms within its boundaries
Ecologists Study Pattern and Process at different ecological levels
- Individual: birth and death events
- Population: rates of birth and death, distribution of individuals
- Community: factors that influence the relative abundance of a species
- Ecosystem: flow of energy and nutrients through the physical and biological systems
Ecologists Study Pattern and Process at different ecological levels
- Landscape: factors that influence the spatial distribution of ecosystems and the effect on organisms
- Biome: patterns of biological diversity with geography
- Biosphere: interactions between ecosystems and
field study
an ecologist examines natural patterns across the landscape
- The relationship between two or more variables is studied
- The results suggest a relationship but do not prove cause and effect
an ecologist will test under controlled conditions and controls the independent variable in a predetermined way
field experiment
the test is applied in a natural setting
- In this type of experiment, it is difficult to control other influencing factors
- Results are realistic because they are collected from a natural setting
laboratory experiment
the ecologist has much more control over environmental
- Results may not directly applicable in the field
an integrated set of hypotheses that together explain a broader set of observations than any single hypothesis
Classifying Ecological Data
All ecological studies involve collecting data and drawing conclusions about a statistical population
The part of the population that is actually
observed is the
Data can be:
- Categorical, or qualitative: observations that fall
into separate and distinct categories
- Numerical, or quantitative: data that are a set of
- Nominal data are unordered categories (hair
color, sex)
- Order is important to ordinal data (prereproductive, reproductive, post-reproductive)
- When only two categories exist, categorical data
are referred to as binary
- Only certain values are possible for discrete data
(integer values, counts)
- Any value within an interval is possible with
continuous data (height, weight)
Displaying Ecological Data: Histogram
A frequency distribution is a count of the number of observations (frequency) having a given score or value; display continuous data; observations grouped into
categories; resulting distribution can be displayed as a histogram
Displaying Ecological Data: Scatterplot
used to examine the relationship between two variables or sets of observations; constructed by plotting x (independent variable) and y (dependent variable)
- Positive: y increases with increasing values of x
- Negative: y decreases with increasing values of x
- No apparent relationship between x and y
Human factor
Ecologists distinguish between the basic science of ecology and the application of ecology to understand human interactions with the environment; traditional distinction is difficult to maintain; human population exceeds 7 billion; collective human impact on resources continues to grow; human activities have the potential to change the climate
Eologists need more information to understand fully why an organism lives where it does and how it
fits into its surroundings.
Temperature and moisture are the main limiting factors for both plants and animals on a global scale
The Physical Environment
• Living organisms require certain physical conditions to survive and reproduce; organisms interact with the physical environment over two very different timescales
- Over many generations as a guiding force of natural selection and over shorter periods to influence an organism's physiology and resource availability
is the ability of the physical environment to support life
Distribution of Biomes
Temperature regime and pattern of precipitation determine
global distribution of the biomes
Climate at macro and micro levels
Macro: Latitude (distance north or south of the Equator, measured in degrees), altitude (elevation especially above sea level or above the earth's surface), land/water ratio
Micro: Surface properties (ex. vegetation), topography (the surface features of a place or region, includes hills, valleys, streams, lakes, bridges, tunnels, and roads), organisms present
Weather and Climate
Both weather and climate refer to the conditions of a place, e.g. temperature, rainfall, snowfall and wind strength
-Refers to a short-term conditions of a particular place, can change from hour to hour, day to day, week to week and season to season
- Fluctuations that arise from internal instabilities of the atmosphere, effects are immediately felt
- Refers to long-term average pattern of the weather condition in a given place/region
- Long-term data are needed to detect any change in the climate
- To describe climate accurately, we need more than an average, i.e. variation, pattern and extremes
Earth Intercepts Solar Radiation
• Earth's weather patterns (e.g., distribution of rainfall) are influenced by the solar radiation intercepted by Earth's atmosphere and the Earth's rotation and movement (ex. prevailing winds and ocean currents)
Solar Radiation
.• the electromagnetic energy or stream of photons produced by the sun measured in terms of
- Wavelength: the physical distance between successive wave crests
- Frequency: the number of crests that pass a given point per second
Earth Intercepts Solar Radiation
• All objects emit radiant energy and the energy emitted depends on the temperature of the object it is coming from
• The hotter the object is, the more energetic the photons and the shorter the wavelength
- Shortwave radiation: emitted by a very hot surface (e.g., Sun = 5800°C)
- Longwave radiation: emitted by a cooler object (e.g., average Earth = 15°C)
Earth Intercepts Solar Radiation
• 51% of the solar radiation that reaches the top of the Earth's atmosphere is actually absorbed by Earth's surface
• The remaining solar radiation is primarily reflected (albedo) and scattered by the atmosphere and clouds
the fraction of solar radiation that is reflected off the surface of an object
Earth Intercepts Solar Radiation
Earth intercepts shortwave solar radiation, which easily passes through the atmosphere and is emitted back as long-wave radiation
- shortwave (solar) radiation is only received during the day but Earth radiates energy longwave both day and night
Greenhouse effect
Energy of long wavelengths can't readily pass through the atmosphere; Earth's atmosphere captures most of the radiation emitted and this energy is radiated back to Earth
Earth Intercepts Solar Radiation
The sun emits electromagnetic radiation of a wide range of wavelengths (400 to 700 nanometers make up visible light)
• These same wavelengths are also called photosynthetically active radiation (PAR) and are used by plants to power photosynthesis
Intercepted Solar Radiation Varies Seasonally
• The amount of solar radiation intercepted at any point on Earth's surface varies by latitude with a gradient of decreasing temperature from the equator to the poles
• At higher latitudes, solar radiation hits Earth's surface at a steeper angle; sunlight is spread over a larger area and radiation must pass through a deeper layer of air (encounters more particles in the atmosphere and is reflected back into space)
Intercepted Solar Radiation Varies Seasonally
Energy input to atmosphere & Earth's surface via solar
radiation drives the annual temperature maximal at equator (maintained by clouds and rainfall) and declines to 40% of maximal values at high latitudes.
Result of:
- Earth's tilt (inclination) of 23.5°
- Earth's movement (24-hour rotation and annual movement around the Sun)
Diurnal cycle
hours of daylight and darkness, varies with the season everywhere on Earth except at the equator (receives 12 hours of daylight and night throughout the year)
Intercepted Solar Radiation Varies Seasonally
- Equator during the vernal equinox and autumnal equinox
- Tropic of Cancer (23.5°C north latitude) during the summer solstice
- Tropic of Capricorn (23.5°C south latitude) during the winter solstice
The seasonality of solar radiation, temperature, and day length increases with latitude (ex. Arctic and Antarctic circles--66.5° north and south latitudes--day length varies from zero to 24 hours over the course of the year), variation in the exposure of different latitudes to solar radiation controls mean annual temperature around the globe
Altitude and temperature
Temperature decreases with an increase in altitude (elevation); influenced by energy emitted from Earth's surface and by atmospheric pressure, causing air to rise and sink; movement of air masses; heat neither gained or lost
Topography Influences Regional and Local Patterns of Precipitation
• Mountainous topography influences local and regional precipitation patterns
• A rain shadow forms on the side of a mountain as an air mass rises, cools, and precipitates. This loss of moisture from results in dry air descending from the other side of the mountain
•Wind, temperature and ocean currents produce global patterns of precipitation
Global Hydrologic (water) cycle between Earth and atmosphere Cycle
• Water is essential for life (75-95% weight of living cell)
• Over 75% of the Earth's surface is covered by water (Oceans contain 97%, polar ice caps and glaciers contain 2%, freshwater in lakes/streams/ground make up less than 1%.)
Hydrological Cycle
•process by which water travels from one reservoir to another (river to ocean, ocean to atmosphere);uses physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow; water goes through
liquid, solid, and gas phases
• Solar radiation is the driving force; provides energy for the
evaporation of water
Hydrological cycle
• Precipitation
• Interception
• Infiltration
• Groundwater recharge
• Runoff
• Evaporation
• Transpiration
sets the water cycle in motion; water vapour circulating in the atmosphere falls to the Earth as precipitation (rain, snow, sleet, slush, hail); falls on soil, bodies of water
the capture of raindrops by plant cover, dead organic matter, urban structures, and streets which prevents direct contact with the soil or bodies of water
precipitation that reaches the soil and moves into the ground; rate depends on type of soil, slope, vegetation, and intensity of precipitation
Groundwater recharge
water entering soil seeps down to an impervious layer of clay or rock to collect
water that flows over the ground surface rather than soaking into the ground
the process of extracting moisture and converting water from the liquid phase to the gas phase
the evaporation of water from internal surfaces of leaves (stomata), stems, and other living parts
total amount of water from the surfaces of the ground and vegetation (evaporation + transpiration)
• atoms are asymmetrically bound to one another
• H atoms share an electron with the O atom via covalent bond (electrons are unequally shared and spend more time around oxygen, water is considered a polar molecule)
• due to polarity, water molecules bond with one another due to hydrogen bonding
The unique properties of water molecules
1. High specific heat capacity
2. High heat of fusion/evaporation
3. Cohesion and Adhesion
4. Surface tension
5. High viscosity
6. Solvent of life
High specific heat capacity
number of calories to raise 1g H2O 1 degree Celsius; can store tremendous quantities of heat energy with a small rise in temperature; thermal regulation in organisms (75-95% H2O); takes a long time to heat large bodies of water and change states (prevents seasonal fluctuations of aquatic habitats;
high heat of fusion/evaporation
the amount of energy required to change a substance from the solid phase to the liquid phase at its melting point; requires a lot of energy to overcome the attractive intermolecular forces (H bonding) to convert molecules to the vapour phase
Cohesion and Adhesion
cohesion allows the water to stick together and resist external forces that would break the bonds (so the water molecules "pull" the other molecules behind them). Adhesion allows the water molecules stick to stick the walls so they do not slip
Surface tension
a phenomenon that results in an inward pull among the water molecules due to strong intermolecular force (H bonds) that brings the molecules on the surface closer together
High viscosity
property that measures the force necessary to separate molecules; due to water's high density , it limits the mobility of organisms
Solvent of life
almost all organic molecules dissolve in it
The importance of water to organisms
1. Growth - cellular expansion (osmotic balance, vacuole )
2. Energy balance - temperature regulation (high specific heat capacity)
3. Solute transport - nutrients, sugars (across phospholipid membrane)
4. Biochemical functions - photosynthesis, cell respiration
5. Structural integrity - turgor pressure (pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell)
Soil: A mixture of mineral and organic materials that is capable of supporting plant life recyles nutrients; controls fate of water; habitat for animal life
made up of:
• Mineral Particles: anchorage, storage, sources and exchange sites for nutrients
• Organic Matter: nutrient exchange, storage, energy for microbes
• Soil Water: source of plant water, transport of soil nutrients.
• Soil Air: O2 to support root respiration, CO2 sink, source of N2 for fixation and eventual uptake.
Soil Formation
• Parent material is the material from which soil develops
- properties determined by the original characteristics of the parent material
• Biotic factors contribute to soil formation (plant roots hasten the process of weathering and pump nutrients from the soil depths up to the surface; through photosynthesis plants return some of the sun's energy to the soil in the form of organic
carbon; through decomposition, dead plants and animals
become organic matter incorporated into the soil)
Soil Formation
• The climate (temperature, precipitation, winds) affects physical/chemical breakdown of parent material; shape soil development
• Considerable time is required for soil to form
the movement of solutes through the soil
(contour of the land) affects erosion (influences amount of water entering soil), deposition, and the influence of climate (gradient of slope)
Characteristics of Soil
Distinguished by colour, texture and depth. Soil color is an easily defined and useful characteristic of soil (it has little influence on soil function)
- Organic matter (humus) is dark or black
- Iron oxides are yellowish-brown to red
- Manganese oxides are purplish to black
- Quartz, kaolin, gypsum, and carbonates are whitish and grayish
Characteristics of Soil
• Soil texture is the proportion of differentsized soil particles
- Gravel > 2.0 mm
- Sand = 0.05 to 2.0 mm
- Silt = 0.002 to 0.05 mm
- Clay < 0.002 mm
• Soil texture affects pore space and the movement of air and water in and through the soil
Characteristics of Soil
Soil depth varies and depends on many factors
- Slope
- Weathering
- Parent material
- Vegetation
• Shallow soils: forests, ridgetops, and steep slopes
• Deep soils: grasslands, bottom of slopes, and alluvial plains
Soil Horizons
Organic layer (O):dominated by organic matter; undecomposed or partially decomposed plant material
Topsoil (A): mineral soil from parent material; organic matter leached from O horizon (dark colour)
Subsoil (B):mineral materials accumulate and salts leached from topsoil (red-brown)
C horizon (C): unconsolidated material underlying the subsoil and extending towards the bedrock, parent material from which the soil developed
The Organism and Its Environment
• The structure and function of an organism reflects its adaptations to its environment
• Each environment presents a different set of constraints on survival, growth, and reproduction
• All organisms must assimilate, reproduce, and respond to external stimuli, but the solutions for each function are unique
The Organism and Its Environment
• The most fundamental constraint on life is energy acquisition
Solar energy -> photosynthesis -> consumption
primary producers are those organisms that derive their energy from sunlight, e.g. green plants, algae
secondary producers are organisms that derive energy from consuming other organisms, e.g. animals
Natural selection
is the differential success (survival and reproduction) of individuals within the population; product of two conditions
- Variation occurs among individuals within a population is heritable characteristic
- Variation results in differences in individual survival and reproduction (changes in properties of populations of organisms over generations)
• The fitness of an individual is measured as its contribution to future generations
• Evolution is the process by which the properties of populations change over generations
• An adaptation is a heritable trait that develops in response to environmental conditions
Example of adaptation
• The target of selection is the phenotype that is directly acted upon by selective forces (beak size for Galapagos finches)
• The selective agent is the environmental pressure that results in fitness differences among individuals (seed size and abundance for Galapagos finches)
• Finches with larger beaks were more likely to survive and reproduce, so there was a shift in the distribution of beak sizes in the population
Types of natural selection
• Natural selection can have different effects on the distribution of a population's phenotype
- Directional selection occurs when the extreme value of a trait is favored
- Stabilizing selection occurs when the mean value of the trait is favoured
- Disruptive selection occurs when members of a population are subjected to different selection pressures
Adaptive constraints
• The Earth is not a homogeneous environment
• Each combination of environmental conditions presents a unique set of constraints on the organisms that inhabit it
• Natural selection favors different phenotypes under different environmental conditions (natural variation of beak size of Galapagos finches and seed size and availability); involves multiple traits and loci
Adaptive radiation
process in which one species gives rise to multiple species
that exploit different features of an environment (food, habitat)
Solar radiation
Energy is inversely proportional to wavelength; maximum emission from the sun at 0.5 μm wavelength; band from 0.40 - 0.70 (micrometers) is photosynthetically active radiation PAR)
Attenuation of Light
Attenuation refers to the reduction of intensity as light passes through some media ( Atmosphere--clouds, gases, water vapours and dust; water; vegetation)
Attenuation of Light
forest:10% reflected to canopy, 1 big amount and 2 little amounts for photosynthetic species
meadow: 20% reflected to canopy, 2 big amounts and 1 little amount for photosynthetic species
Plant Cover Influences the Vertical Distribution of Light
The vertical gradient and quality of light in terrestrial environments are determined by the absorption and reflection of solar radiation by plants
• Number, size, and shape of leaves
- Leaf area (of flat leaves) = surface area of one or both sides
- Leaf area index (LAI) = the area of leaves per unit ground area
• Cumulative leaf area and LAI increase as you move from the top of the forest canopy to the ground, vice versa for PAR (i.e. decreases)
Beer's Law and the Attenuation of Light
The greater the surface area of leaves, the less light will penetrate the canopy and reach the ground; the quantity of light attenuated per unit of leaf area index
• The attenuation (vertical reduction) of light through a
stand of plants is estimated using Beer's law.
- ALi is light reaching any vertical position (i) expressed
as the proportion of light reaching the top of the canopy and is equal to the natural logarithm (2.718) of the leaf area index above height i multiplied by the light extinction coefficient
The availability of light directly influences the levels of photosynthesis;the process by which the Sun's energy (shortwave radiation) is used to fix CO2 into carbohydrates (simple sugars) and release O2
6 CO2+ 6 H2O (+ Sun's energy) = C6H12O6 + 6 O2
• products of photosynthesis are used in respiration
C6H12O6+ 6 O2 = 6 CO2 + 6 H2O + Energy
Photosynthetic Activity
• Net photosynthesis = Photosynthesis -Respiration
• The availability of light, photosynthetically active radiation (PAR), to the leaf directly influences the rate of photosynthesis
• The light compensation point (LCP) is the point at which the rate of net photosynthesis is zero
• The light saturation point is the point above which no further increase in photosynthesis occurs
• Photoinhibition is the negative effect of high light levels, e.g. shade environments
involves diffusion and transpiration; CO2 diffuses from the atmosphere to the leaf through pores called stomata; results in water loss that must be pulled up from the soil using transpiration (through the shoot system and back into leaves)
Species of Plants Are Adapted to Different Light Environments
The presence of other plants greatly influences the amount of PAR that each receives
• Sun versus shade plants (Shade plants tend to have a lower light saturation point and a lower maximum rate of photosynthesis)
Species of Plants Are Adapted to Different Light Environments
• Differences in the performance of sun versus shade plants are related to rubisco (costly molecule for a plant to manufacture)
• Shade plants produce less rubisco which reduces energy cost and leaf respiration rate and produces more chlorophyll
- Lowers photosynthesis rate = Lower light compensation point
- Restricts maximum photosynthetic rate because there is only so much rubisco available to fix CO2
Species of Plants Are Adapted to Different Light Environments
Similar trends documented for all nine species grown under high versus low light conditions
• Seedlings grown under low light conditions had or experienced a:
- Lower rate of leaf respiration
- Decrease in light compensation point
- Decrease in maximum rate of net photosynthesis at light saturation
- Greater specific leaf area (SLA: cm2/g) larger
and thinner
• A measure of leaf biomass allocation
- Greater allocation of carbon to leaf production and less to roots
Sun and Shade Leaves Structural Characteristics
Characteristics: Sun Leaf vs Shade Leaf
Leaf Area - +
Mesophyll Thickness + -
Cell Number + -
Stomatal Density + -
Chloroplast Number + -
Lobed + -
Sun and Shade Leaves Chemical Characteristics
Characteristics: Sun Leaf vs Shade Leaf
Leaf Dry Matter - +
Energy Content + -
Water Content - +
Starch + -
Sun and Shade Leaves Functional Characteristics
Characteristics: Sun Leaf vs. Shade Leaf
Photosynthetic Capacity + -
Respiratory Intensity + -
Transpiration + -
Plant adaptations to high and low light
Phenotypic adaptations and plasticity allow plants to respond to different light environments. Shade plants have low photosynthetic, respiratory, metabolic and growth rates compared to shade-intolerant plants. Leaves in sun plants are small, lobed and thick while leaves in shade plants are large and thin
Water Potential
• Water potential is the measure of the free energy of water
- Pure water (no solute content) has the greatest amount of free energy; as pure water accumulates solutes or atmospheric relative humidity drops below 100 percent;free energy of water declines and becomes -ve
• Water moves from a higher to lower potential
- atm potential<leaf potential<root potential <soil potential
Water Moves from the Soil, Through the Plant, to the Atmosphere
• The rate of water loss varies daily (humidity, temperature)
- Plant characteristics (stomata opening and closing)
• The water-use efficiency is the ratio of carbon fixed (photosynthesis) per unit of water lost (transpiration)
- Terrestrial plants must balance intake of CO2 with
the loss of water
Water Potential
Free energy of water sample compared to free energy of pure
Free energy = capacity to do work
H20 - moves high potential (0 or small -ve) to low (-ve)
Generally H20 in biosphere potential < 0 (not 100% humidity)
Components include solutes, matric forces and turgor
Categories of plants
Hydrophyte: a plant that is adapted to living in either
waterlogged soil or partially/wholly submereged in water.
(e.g. aquatic plants, water lillies

Mesophyte: a plant without adaptations to environmental
extremes (e.g. forest understorey herb, purple bluets)

Sclerophyte: a plant that is adapted to drought by producing
thick, tough leaves (sclerenchymatous). (e.g. Mediterranean
Categories of plants
Xerophyte: a plant that is a adapted to living in dry conditions caused by a lack of soil water (physical drought) or heat/wind bringing about excessive transpiration (physiological drought), e.g. plants from desert

Succulent: a plant that is adapted to drought by storing large
quantities of water in large parenchyma cells (e.g. desert/dune cacti, prickly pear cactus).
Temperature Regulation - two physiological strategies
• In endothermy, animals generate heat metabolically, and this results in the maintenance of a fairly constant internal temperature independent of external temperatures (homeothermy) ex. birds, mammals, warm blooded organisms
• In ectothermy, animals acquire heat primarily from the external environment (poikilothermy) ex. fish, amphibians, reptiles, insects, and other invertebrates, also cold blooded organisms (environmental temp controls rate of metabolism)
Temperature Regulation
• Ectotherm and endotherm emphasize the mechanisms that determine and regulate body temperatures
• Homeotherm and poikilotherm represent the nature of body temperature — constant or variable
Temperature Regulation
• Heterotherms are animals that regulate body temperature by both endothermy and ectothermy, depending on environmental situation and metabolic need (bats, bees, and hummingbirds)
Homeotherms Escape the Thermal Restraints of the Environment
• Homeotherms maintain body temperature by oxidizing glucose in cellular respiration
- Oxidation is not completely efficient and some energy is lost as heat
• Homeothermic respiration rate is proportional to body mass
Homeotherms Escape the Thermal Restraints of the Environment
• The thermoneutral zone is a range of environmental temperatures within which the metabolic rates are minimal
• Metabolic rate increases beyond the critical temperatures above and below the thermoneutral zone
Homeotherms Escape the Thermal Restraints of the Environment
• Homeotherms maintain a high level of energy through aerobic respiration
- They can sustain high levels of physical activity for long periods
• Homeotherms regulate exchange between the body and environment by insulation
- Fur: barrier to heat flow, insulation value varies with thickness
• Fur thickness changes with the seasons (feathers and body fat)
Homeotherms Escape the Thermal Restraints of the Environment
Homeotherms regulate exchange between the body and environment by evaporative cooling (sweating, panting and gular fluttering; wallow in water and wet mud)
Thermoregulation - Morphology
Allen's Rule
The extremities of homeotherms in cold environments are smaller than those of members of the same or related species of hot environments
Thermoregulation - Morphology
Bergman's Rule
The body size of homeotherms in cold environments is greater than those for individuals of the same or related species in warm environments
Behavioural Adaptations to Drought
poikilotherms exploit variable microclimates by moving into warm, sunny places to heat up and seek shade to cool; raise or lower their body to increase or decrease conductance
Physiological Adaptations to
derive water from food (seeds), do not sweat or pant to keep cool, specialized kidneys allow excretion of waste with
very little water loss, nocturnal - spend days in burrows
Trade-offs in thermal regulation
homeotherms are able to remain active regardless of temperature (high rate of metabolic activity= high energy cost); places a lower limit on body size. Due to the low metabolic cost, poikilotherms can curtail metabolic activity in times of food and water shortage as well as temperature extremes (able to colonize in those areas)
total of all biotic and abiotic factors that determine how an organism fits into its environment; where and how does an organism live and function (habitat and role in community)
might be strained by interspecific competition (competition with different species). When they use the same resources their niches overlap (may or may not be competitive). Competition results in the niche compressing or shifting, absense of other species results in niche expanding.
Fundamental niche
Fundamental Niche: All possible environmental conditions that an organism can live; the niche potentially occupied by that species (where a species could live); presence of different species reduces fundamental niche to realized niche
Realized niche
the niche actually occupied by that species at a given time and space (with competition from other species, where a
species does live); may not provide optimal conditions
• aggregates of individuals
•definitive growth form
• group of individuals of the same species that inhabit a given area
• have distribution & abundance (changes in space and time due to dispersal, immigration and emmigration), age structure, different sex ratios, etc
Population parameters
• Natality
• Mortality
• Immigration/Emigration
production of new individuals by birth, hatching, germination.
- Fecundity: potential ability of an organism to produce offspring.
- Fertility: number of viable offspring produced during a period of time.
death of individuals in the population.
- Potential Longevity: maximum lifespan attainable by an organism
- Realized Longevity: the actual lifespan of an organism
Movement of individuals from one population to another
Unitary Organisms
Organisms in which populations are comprised of recognizable individual units. Form, development, growth and
longevity are predictable and determinate.
Genet: A separate genetically unique individual arising from a
zygote (sexual reproduction). This is the only possibility
(ecologically) for unitary organisms.
Modular Organisms
In modular organisms, the zygote develops into a unit of
construction (a module) that then produces further, similar modules. Modules produced asexually by the genet are ramets (may be physically linked to the parent or separate; exact copies of the parent genet) ex. plant
Distribution of a Population
• Geographic range
• Barriers
• Food production
• Water supply
• Habitat
• Incidence of parasites, pathogens and
• Geographic barriers
Direct: climate e.g. temperature, precipitation
Indirect: resources availability
Geographic range
Area that encompasses the all individuals of a species
The number of individuals in the population; defines population size; is a function of population density and the area over which the population has been distributed (number of individuals
per unit area or per unit volume)
• Crude density(number of individuals per unit area; area over which the population is distributed)
Population Distribution Patterns
1. Random - an individual's position is independent of others
2. Uniform - results from negative interaction among individuals or uniform distribution of resources
- Uniformly spaced among individuals.
- Exclusive use of areas
- Individuals avoid one another.
3. Clumped - results from patchy resources, social groupings, ramet dynamics
- Mutual attraction among individuals
- Patchy resource distribution
The Distribution of a Population Defines Its Spatial Location
• Individuals are not distributed evenly throughout the geographic range of a population
• Individuals can only occupy areas that can meet their requirements
• Can vary from location to location
• Distribution of individual in a population, clumped, random, uniform etc.
• Estimates going to be different from a sample
Estimating Population Size or Density
• Census of the whole population
• Sampling: random, systematic, stratified
• Sampling for mobile animals - Capturerecapture
• Indirect methods
- Index of relative abundance
Determining Density Requires Sampling
• Population size = density x area
- In most cases, population density must be estimated by sampling a portion of the population
• Sampling methods for plants and sessile animals
- Counting the organisms in a subsample (quadrats)
- Abundance estimates may be skewed by a clumped spatial distribution (cluster in group)
Determining Density - Markrecapture Method
• Sampling methods for mobile animals using Peterson (Lincoln) Method
- Capture-recapture or mark-recapture methods are based on trapping, marking, and releasing a known number of marked animals (M) into the population (N)
- Some time later, the same population is sampled and the ratio of marked (R) to sampled (n) individuals in the second sample represents the ratio for the entire population
• N/M = n/R
Determining Density - Markrecapture Method
The Peterson (Lincoln) Method:
1. Establish a sampling frame and locate samples (traps)
2. Run trapping period and mark all trapped individuals
3. Release marked animals back into population
4. Run a second trapping period
5. Record the number of marked individuals in the second trapping period.

(Marked animals in second sample (R)/Total caught in second sample (n)) = Marked animals in first sample (M)/Total population size (N)
Determining Density - Markrecapture Method
• Assumes equal chance of capture for all individuals in the population
• Study population is "closed"
- No deaths or births; no emigration or immigration (between marked, released and recaptured)
- Same birth or death rate (both marked and unmarked)
• Marked animals randomly mixed up among unmarked individuals
• No loss of marks (no marks fall off)
• Other factors include time of capture, stress of capture, sex, age, illness etc
Determining Density Requires
Indirect sampling methods
- The presence of individuals of a particular species can be determined by counts of vocalizations, scat, tracks, or some other sign of
- These counts are called indices of abundance
Populations Have Age Structures
• proportion of individuals in different age classes
• determined by aging its members
• is influenced by reproduction and mortality and bears on the rate of population growth
- Prereproductive
- Reproductive
- Postreproductive
• The length of time that an individual remains in each stage depends on its life history
- Short-lived versus long-lived organisms
Populations Have Age Structures
• Techniques used for aging animal populations
- Mark young individuals and follow their survival
- Study a representative sample e.g. carcasses
- Tooth wear, replacement of teeth
- Plumage changes (for birds)
- Growth rings in teeth, horns, ear bones, etc
- Mark individual seedlings and follow them through their lifetimes
- Diameter at breast height (dbh) - trees and shrubs
- Counting annual rings - trees and shrubs
Populations Have Age Structures
• Age pyramids represent the age structure of a population at some period in time
• The age structure is a product of the age-specific patterns of mortality and reproduction
• Plant populations: the distribution of age classes is often skewed because dominant overstory trees may inhibit the establishment
of seedlings or the growth and survival of juvenile trees
Sex ratios in populations shift with age
•Populations tend toward a 1:1 sex ratio
• Differences in life expectancy can alter this ratio (Male rivalry, risk of predation)
• For example, in mammalian population,
at birth <15. 1.05; 15, 1.04; 15-65, 1.02;>65 , 0.81
Individuals Move Within the Population
• dispersal directly influences individual's local density
- Metapopulation dynamics
- This maintains gene flow between subpopulations
• One-way movement of individuals
- Emigration is when an individual moves out of a sub-population
- Immigration is when an individual moves into a
• Distribution and abundance of population change with space and time
• Primary factors driving the dynamics of population abundance are the demographic processes of birth and death.
• Many causes such as: dispersal, immigration, emigration, and temporal changes in environmental conditions.
• Population- an interbreeding group of individuals of a single species that occupy the same general area
• Populations have size and geographical boundaries
- The density of a population is measured as the number of individuals per unit area
- The dispersion of a population is the pattern of spacing among individuals within the geographic boundaries.
• Population has parameters ( Births, immigration, emigration, deaths)
Population Characteristics
• Size (abundance)
• Density
• Dispersal
• Age structure
• Sex ratio
• Rate of birth and death (rate of growth)
Population Growth
Hw the number of individuals in a population increases or decreases with time
- Individuals added via birth and immigration
- Individuals removed via death and emigration
• Immigration and emigration occur in open populations, but not in closed populations
Open and Closed Populations
• In closed populations, changes in abundance (N) are determined by births (B) and deaths (D).
Nt+1 = Nt + (Bt - Dt)
• In open populations, changes are further influenced by emigration (E) and immigration (I).
Nt+1 = Nt + (Bt - Dt) + (It - Et)
• Change in abundance over time is described by a rate.
• Time frame of measurement can be continuous or discrete
Discrete vs Continuous
1) With discrete generations.
- Single breeding season, live for 1 year.
- Each female produces an average number of female offspring each year
- R0 is net reproductive rate.
2) With overlapping generations.
- Prolonged breeding or continuous breeding season.
- Growth depends on the conditions at the current moment.
- r is per-capita rate of population growth
Population Growth with Overlapping Generations
• A (closed) population
- Will increase as a result of new "births"
- Will decrease as a result of "death"
• Birth and death are continuous
b = the proportion new individuals producing per unit of time i.e. birth rate
d = the proportion of individual dying per unit of time i.e. death rate
r = instantaneous rate of population growth i.e., r = b - d, where b and d are the instantaneous birth and death rates
Population Growth
the change in population size over time is equal to the birth rate- the death rate d is the number of death rate x population size which is equal to the instantaneous (per capita) rates of birth and death of the population size
Exponential Population Growth
• Exponential growth rate
- When r = 0, there is no change in population size
- When r > 0, the population increases exponentially
- When r < 0, the population decreases exponentially
• Exponential growth results in a continuously accelerating (or decelerating) rate of population increase (or decrease); initial population is small and no food or resource limitation
Population Growth with Overlapping Generations
Exponential population growth is population increase under idealized conditions
• Under these conditions, the rate of increase is at its maximum, where r is denoted by rmax
• Exponential growth not sustainable over a long time under most natural conditions for any population.
• Observed only when starting with small numbers
Population Growth with Overlapping Generations - Carrying Capacity
• Carrying capacity (K) is the maximum population size
the environment can support
• Carrying capacity varies with the abundance of limiting
• As resources are depleted, population growth rate slows and
• Finite amount of resources can only support a finite number of individuals.
• Logistic population growth is modeled as a Sigmoid (S-shaped) population growth curve.
Logistic Model of Population Growth
When the population is small (N < K), it increases rapidly, at a rate slightly lower than that predicted by the exponential model
- The rate of population growth is greatest at the inflection point, when N = K/2.
- As N approaches K, the rate of population growth begins to slow
- If N = K the population growth rate is zero
- If the population size exceeds K, the population size will decline until it reaches K
Use logistic model
• In early growth stages.
- Harvesting fish or game--when is the most efficient time to
• Determining carrying capacity.
- Stable populations--what happens when resources are
Reproductive Strategies
• Resource allocation for reproduction
• Timing (once or many times)
• Few or many: Limited resources and environment pose major restrictions (size)
• Parental survivals
Reproductive Strategies
Semelparity (one time)
- Organisms that carry one time reproductive events,
Iteroparity (multiple)
- Organisms that produce off spring more than once
over their lifetime.
Reproductive Strategies
• Organisms that produce many offspring have a minimal investment in each offspring.
• They can afford to send a large number into the world with a chance that a few will survive. By so doing, they increase parental fitness but decrease the fitness of the young.
•Type I:individuals have long life spans, survival rate is high
throughout the life span with heavy mortality at the end; produce few young but care for them well
•Type II: fairly steady death rate throughout life (survival rates do not vary with age); usually a result of chance processes
over which the organism has little control
•Type III:produce large numbers of young which receive little or no care; mortality rates are extremely high in early life; survival of young is dependent on luck; once settled prospects of survival are better
rate of increase (r-selection) organisms
- Characteristic of high population growth rate
- Unpredictable/unstable environments
- High rate of growth
- Numerous individuals rapidly produced
rate of increase (r-selection) organisms
1. Have a Boom-and-Bust Life Cycle
2. Have short life spans
3. Produce many offspring
4. Smaller organisms
5. Don't maintain a population near carrying capacity
6. Controlled by densityindependent factors
rate of increase (r-selection) organisms
• Selection acts to maximize "r" (intrinsic rate of natural increase)
• r-strategists are able to colonize temporary habitats or disturbed habitats where competition is minimal
• Rapid and abundant reproduction
• Short life span
• Typically opportunists
carrying capacity (k-selection) organisms
- characteristics of efficient resource use
- Predictable/stable environments
- High competitive ability
- Fewer larger individuals slowly produced
carrying capacity (k-selection) organisms
1. Have long life spans
2. Produce few offspring that have a better chance of
living to a reproductive age
3. Are larger organisms
4. Maintain a population at or near k
5. Controlled by densitydependent factors
carrying capacity (k-selection) organisms
• K - as in the carrying capacity term in the logistic equation (logistic population growth).
• Allocate more resources to competitive ability and survival mechanisms; less to reproduction.
• Longer life spans.
• Resource-limited.
• Poor colonists - lack means for wide dispersal
Population Growth
In a population with no immigration or emigration, rate of change in population size through time over a defined time interval is a function of the difference between the rates of birth and death. When the birth rate exceeds the death rate, the rate of population change increases with population size.
Population Growth
As the time interval over which population change is evaluated decreases, approaching zero, the changing population size is expressed as a continuous function, and the resulting pattern is turned exponential population growth. The difference in the instantaneous per capita rate of birth and death is defined as r, the instantaneous per capita growth rate
Logistic Population Growth
Because resources are limited, exponential growth cannot be sustained indefinitely. The max population size that can be sustained for a particular environment is termed the carrying capacity (K). The logistic model of population growth incorporates the concept of carrying capacity into the previously developed model of exponential growth. The result is a decrease in their rate of population growth as the population size approaches the carrying capacity.
Density-dependent regulation
Populations do not increase indefinitely. As resources become less available to an increasing number of individuals, birth rate decreases, mortality increases, and population growth slopes. If the population declines, mortality decreases, births increase, and population growth speeds up.
Global Warming
Individuals are the functional units in ecology
• How these individuals are interacting to their surrounding environments
• An adaptation is a heritable trait that develops in response to environmental conditions
• Currently, environment is changing rapidly i.e. climate change
10 indicators of a warming world
1. increase humidity
2. increase temperature over oceans
3. increase sea level
4.increase ocean heat content
5.increase temperature over land
6. increase air temperature near surface
7. decrease sea ice
8. decrease glaciers
9. decrease snow cover
10. increase sea surface temperature
Living things are intimately connected to their
physical surroundings
Ecosystems are affected by changes in:
- temperature
- rainfall/moisture
- pH
- salinity (saltiness)
- activities & distribution of other species
Ecological impacts
As a result of climate change, species and ecosystems are experiencing changes in:
- ranges
- timing of biological activity
- growth rates
- relative abundance of species
- cycling of water and nutrients
- the risk of disturbance from fire, insects, and invasive
Range shifts
Species are relocating to areas with more tolerable climate
Range shifts particularly threaten species that:
- cannot move fast enough
- depend on conditions that are becoming more rare (like sea ice)
Timing of activities
Some seasonal biological activities are happening 15-
20 days earlier than several decades ago:
- Trees blooming earlier
- Migrating birds arriving earlier
- Butterflies emerging earlier
Changes in timing differ from species to species, so
ecological interactions are disrupted.
Role of Humans
Compounding Factors
• Human activities have many other effects on ecosystems.
• These effects compound the effects of climate change,
making it more difficult for ecosystems to adapt.
- Pollution
- Habitat fragmentation
- Invasive species
- Overfishing
- Manipulation of water sources
Role of forests and forestry in carbon cycle
- Less than half of human emissions stay in atmosphere
- Reduce emissions Or Reduce sources
- Mitigation = reduced sources and/or increased sinks
- Forests/forestry can have significant impacts on future
atmospheric C concentrations
Competition in Nature: Niche Partitioning
Species can coexist only if there is a partitioning of available
resources to reduce or eliminate competition for one or
more limited resources
• Predation is the consumption of one living organism (the prey) by another (the predator)
• Interaction through regulating each others
- predators may regulate prey populations (mortality), and
- prey may regulate predator populations (growth rate)
Predation forms
• Categories of heterotrophic organisms
- Carnivore
- Herbivore
- Omnivore
• Functional classifications of predator
- True predator
- Grazer/browse
- Seed predator/planktivore
- Parasite
- Parasitoid
- (Cannibals)
Predation forms
• A predator (true predator) kills its prey immediately upon capture, consumes multiple prey organisms, and functions as an agent of mortality on prey populations

• Most herbivores (e.g., grazers and browsers) consume only part of the plant and usually do not kill the plant
- Seed predators and planktivores function as true predators
Predation forms
• Parasites feed on the prey organism (host) while it is still alive, and their feeding activity is generally not lethal in the short term
- This is a very intimate relationship between parasite and host
• Parasitoids lay eggs on a host and when these eggs hatch, the larvae feed on the host, slowly killing it
• Cannibals kill individuals from their own population, e.g. tadpoles
The two populations rise and fall in oscillations
• Each population functions as a densitydependent regulator on the other
- Predator: density-dependent regulation (mortality)
on prey
- Prey: density-dependent regulation (birthrate) of
• The two populations rise and fall in oscillations
• The cycle can continue indefinitely — the prey is never quite destroyed; the predator never completely dies out
Predation in Complex Systems
Food Shortage: Carrying capacity (as density goes up
Predator Regulation: Equilibrium set by the predator
Population Regulation
• The relationship between the per capita rate of consumption and the number of prey is the predator's functional response
- The greater the number of prey, the more the predator eat
• An increased consumption of prey results in an increase in predator reproduction, and this is the predator's numerical response
• Additional factors that influence predator-prey interactions
- Cover or refuges for the prey
- Difficulty of locating prey as it becomes scarcer
- Choice among multiple prey species
- Coevolution
Foraging Involves Decisions about the Allocation of Time and Energy
• Optimal foraging theory considers the trade-offs between conflicting demands (e.g., defense, avoiding predators, mating, caring for young)
• This is based on the hypothesis that natural selection should favor "efficient" foragers, those who maximize their energy or nutrient uptake per unit of effort
• Foraging decisions (cost versus benefit)
- Costs are measured in terms of the time and energy expended in the act of foraging
- Benefits are measured in terms of "fitness"
Foraging Involves Decisions about the Allocation of Time and Energy
Composition of animal diets
- process of choosing what to eat from among choices
• Profitability (of prey):
- net energy gained per unit of handling time = E /Th
(E: energy gained)(Th: handling time - catch, kill and eat a prey)
• Optimal foraging theory predicts that the preferred prey (P1
or P2) will be the one with the greater profitability
Foraging Involves Decisions about the Allocation of Time and Energy
• Predators make decisions such as:
- What types of food to eat?
- Where and how long to search for food?
• Any food item has a benefit (energy content) and a cost (time and energy devoted to search and acquisition)
- Profitability = E / Th
• When faced with a choice, the predator should select the prey with the higher profitability (E / Th)