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227 terms · BIOL 2446 LECTURE


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

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