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ap enviro unit 3
Terms in this set (100)
a group of organisms that is distinct from other groups in its morphology(body form and structure), behavior, or biochemical properties
distinct behavior and structure
species and biodiversity
more species= greater biodiversity
- it is difficult to take measurements so ecologists use estimates through sampling
the total number of species living in a given area
the relative proportion of individuals within different species in a given area
species evenness and richness both
boundaries that separate species
species live in diff geographic location
isolation between populations due to physical barriers
species reproduce at different times
species live in same ecosystem but occupy different niches
Isolation caused by differences in courtship or mating behaviors
physically unable to breed meaning genitalia isnt compatible
gamete (hybrid iviability)
breeding but no fertilization
hybrid forms but cannot have offspring of its own
the study of evolutionary relationships among species
Evolutionary history of a species using morphological chemical and genetic evidence
diagrams that represent evolutionary relationships amongst organisms
a system of classifying organisms based on shared characteristics derived from common ancestry
group of organisms that evolved from a common ancestor and are related
tree diagram based on similarities and differences between species. They show the most probable sequence of divergence in clades they also illustrate when speciation has occurred.
occurs within a species, creating a variety of characteristics
genetic changes that give rise to new species generations, families, classes, or phylageny
codes for a trait - physical location on a chromosome ex.
the complete set of genes of an organism
Genotype can control phenotype, but often the environment also has a role to play in phenotype, especially through behaviors.
the complete set of physical traits of an organism including behaviors, anatomy and physiology.
the ability to survive and reproduce
traits that increase fitness
change in genetic composition of a population over time
3 primary ways of evolution
1. artificial selection
2. natural selection
3. random process
1. Humans choose which traits are most favorable and breed those organisms that express those traits
2. Organisms lacking those traits are removed from the population
3. Organisms that are chosen are not necessarily more fit
Process by which the environment determines which individuals survive and reproduce
Darwin and Wallace both generated this theory
-There is an abundance of organisms in a population
-More organisms are born than can survive
-Individuals differ in their traits
-Differences in traits are heritable
-Differences in traits increase an organism's fitness
Sexual selection is a form of natural selection. Females exhibit preferential treatment for males with specific traits. Generates key differences between males & females
Example: Bird of Paradise,
- New trait appears, if favorable it will increase, if not favorable it will disappear
2. Gene Flow
- Exchange of genes between populations
- Immigration and emigration
- Usually a stabilizing factor- reduces speciation
3. Genetic Drift
-Evolution because of random chance (for example random mating). Two main types: bottleneck effect and founder effect.
a. Bottleneck Effect
- organisms survive a disaster because of random chance, not fitness.
b. Founder effect
-organisms are chosen at random to begin a new population
new species that occurs because of geographic isolation/barriers
A physical barrier isolates species
Over time, the two distinct, isolated populations evolve independent
After enough time, populations can no longer interbreed → new species
Requires geographic isolation which leads to reproductive isolation
Speciation without a divided population.
small change causing ripple effect
One species evolves into two, without a physical, geographic barrier present
Polyploidy- chromosome number increases
Most organisms are diploid meaning they have two copies of each chromosome (maternal and paternal)
Polyploidy results in 3 copies (triploidy), 4 (tetraploidy) or even 6 copies of a chromosome being present
In order to success fertilize, sperm and egg must have same ploidy level, reproductive isolation
Typical in flowering plants like wheat
5 mass extinctions
1. Ordovician: 450 million yrs ago 86% of all life die. most life was in oceans
2. Devonian : 360 milion yrs ago. life on land and ocean, over 70% of all species died
3. Permian: 250 millin yrs ago more than 95% of life died "the great dying"
4. Triassic: 200 million yrs ago pangea broke apart about 75% of all species died
5. Cretaceous: 65 million yrs ago "the k-t extinction" 75% of species died including dinosaurs
Rate of Evolution
- typically occurs over deep time
- Rapid evolution by natural selection
- Usually occurs in response to environmental changes
- Sink or swim; evolve or die
-Requires organisms with short lives and high breeding rates
- Very rapid evolution by artificial selection
-By now having shorter generation times (earlier maturity) -evolution can occur at a faster rate than.
Range of tolerance:
the limits to the abiotic conditions that a species can tolerate
The suite of abiotic conditions under which a species can survive, grow and reproduce. This is more theoretical than practical
the range of abiotic and biotic conditions under which a species actually lives.
a species that can live under a wide range of abiotic or biotic conditions
a species that is specialized to live in a specific habitat or to feed on a small group of species
If species can benefit from environmental change & increase their distribution the opposite must also be true. Those species unable to change will become extinct.
Why do they go extinct?
No favorable environment is available
Competition from other species
Life expectancy of a species
1 million & 10 million years
Fossils are rare because they require specific conditions
No decomposition and rapid burial in mud or sediment → fossilization
Provides a rough estimate of what life looked like in the past. But is not 100% representative.
determined by the # of births & deaths in a population.
Intrinsic growth rate (r)
refers to the maximum growth of a population under ideal conditions & unlimited resources.
Growth is limited by carrying capacity
Sometimes a population can exceed its carrying capacity because of a shift in resources. This is called overshoot.
When a population exceeds its environment's carrying capacity die off will occur to correct the imbalance. During die off, individuals die off rapidly resulting in a reduction in population size.
have low intrinsic growth rates due to having a limited number of offspring at a time & not reaching sexual maturity until late in life.
Quality over quantity
Populations typically follow S curve and stay near carrying capacity (K)
Parental care to ensure survivorship
have high intrinsic growth rates. This is because of their ability to have large numbers of offspring at a time.
Quantity over quality
Named for "r" value
Type I- high survivorship will rapid drop off in old age. Typical of K-selected species
Type II- consistent die off/steady survivorship
Type III- rapid die off of young organisms followed by high survivorship of adults. Typical of r-selected species
Metapopulations occur over large areas with occasional movement between smaller populations.
The sub-populations can be connected by corridors- strips of habitat that link metapopulations together.
When metapopulations fragment
Inbreeding can occur
Small populations are more susceptible to natural disaster and predators.
Carnivores, herbivores, omnivores, detritivores
Competitive Exclusion Principle- Interspecific
Two species competing for the same limiting resource cannot exist
One species will outcompete the other
Evolve to fill a different niche or go extinct
Prey often develop defenses
Behavioral- hiding or reduced movement
Morphological- specialized structures like spines and camouflage
Chemical- emit toxins that harm predators
Keystone species that creates or maintains habitat for other species
Alligators (gator holes)
ecological succession in which soil has been removed
ecological succession that occurs in areas that have been disturbed, but not lost their soil
Rocky intertidal zones can be overturned by tides and storms
Glaciers can carve out lake basins that fill up with water
Over time sedimentation in ponds and lakes form basins
succession species that colonize new areas rapidly and grow well in full sun
succession species that move in early on
grow faster than hardwoods, dominate before being replaced
hardwoods are generally slow growing, but tallest
The first plant community that forms on bare rock often includes organisms such as
lichens and mosses
Latitude affect species richness
increasing latitude results in fewer species because of reduced insolation energy and angle of incidence
time affects species richness
the longer a habitat has existed, the more colonization can occur, resulting in more richness
Theory of Island Biogeography
Habitat size: larger habitats have more species
More likely to be "found" by dispersing species
Can support more species, greater surface area results in greater insolation energy
More environmental conditions results in more niches
Distance from a source of species: less distance → more species
Distant islands are more isolated, less gene flow and immigration/emigration
Two islands of the same size
The one closest to the mainland will have the greatest number of species
Current Human Population Growth
Was stable for a long time (B = D), but exponential growth began about 400 years ago
Death rate dropped, but birth rate remained high
Human population is growing exponentially
Food supply is increasing linearly
Humans will eventually reach carrying capacity
Counter Argument: growing population provides intellect to circumvent restrictions from carrying capacity for example, Technological advancements: agriculture, refrigeration, GMOs
factors that increase population
Births & Immigration
factor that decrease population
Deaths & emigration
changes in population size
(B+I) - (D + E) = change in population size
Study of human populations and population trends
Crude birth rate (CBR):
number of births per 1000 individuals
Crude death rate (CDR):
number of deaths per 1000 individuals
Global population growth rate =
Rate of Natural Increase (RNI)
Rule of 70
If we know growth of pop. & assume it's constant - we can calculate # of years it takes for that population to double.
Doubling time (years) = 70/growth rate (RNI)
The rule of 70 provides an approximate, not exact answer.
Demographic Transition Model
A sequence of demographic changes in which a country moves from high birth and death rates to low birth and death rates through time.
demographic transition model phases
Phase I: Pre-Industrial
Phase II: Transitional
Phase III: Industrial
Phase IV: Post Industrial
both CDR and CBR are high
Lack of medical care, sanitation, clean water
Zero population growth
CBR remains high, CDR begins to fall
Increased access to food, health care, sanitation
Lack of birth control, education
High population growth
CBR begins to fall, CDR decreases
Increased affluence & education
Declining birth rates
Stable population growth
CBR is below the CDR
High affluence & economic development
(increase in CBR)
Negative population growth
Age Structure Diagrams
Visual representation of the number of individuals within cohorts, usually broken down as males vs. females.
Wide base = population growth
Wide top = suggests decline
Total Fertility Rate (TFR)
estimates how many children each woman in a population will have throughout her childbearing years. TFR is an average.
Replacement-level fertility =
TFR required to offset the average number of deaths in a population. Replacement-level fertility maintains a stable population level.
replacement-level fertility is about 2
replacement-level fertility is higher because of higher infant mortality rate
Avg # of years that an infant born in a particular year is expected to live.
Better health care = longer life expectancy and higher resource consumption
In general males have a higher death rate than females
Males tend to make more hazardous decisions
Infant & Child mortality
Infant = less than 1 year old (rate is per 1000)
Child = between 1 and 5 years of age (rate is per 1000)
Nations with high life expectancy & low infant/child mortality tend to have high rates of health care, adequate food supply, good sanitation, clean drinking water & moderate rates of pollution.
Developed nations have low IMR, US (5.9) and France (3.3)
Developing nations have high IMR: Liberia (63) and Bolivia (40)
Can vary by socioeconomic status: 12.4 for African Americans and 5.3 for Caucasians
Aging & Disease
US has a high crude death rate because of large elderly population
Disease has a large impact on crude death rate
Malaria and Tuberculosis were the biggest killers historically
Now HIV/AIDS is the biggest, large impact on infant mortality, child mortality, population growth and life expectancy
Net migration rate = difference between immigration and emigration in a given year per 1000 people
produced by the process of mutation and recombination
when two species divide a resource based on differences in their behavior or morphology
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