Unit D Flashcards
allele frequency
proportion of each allele in a populations gene pool
evolution
the change in genetics over time, not the change in traits in an individuals lifetime.
gene pool
total of all alleles in a population
Hardy-weinberg equilibrium
describes a population in which allele frequencies do not change over time. no microevolution is happening
Hardy-Weinberg Principle
allele frequencies in a gene pool will remain at equilibrium in each generation of a sexually reproducing population if 5 of the following conditions are met:
1. No selection
2. No mutation
3. No migration
4. No small populations
5. Random mating
microevolution
the change in allele frequencies in a population over time
p+q=1
sum of allele frequencies in a population for any gene of any diploid organism.
p^2 + 2pq + q^2 = 1
equation used to describe genotypic frequencies
population
all members of one species occupying a particular area at the same time and that interbreed
Bottleneck effect
extreme example of genetic drift that happens when the size of a population is severely reduced (natural disasters, etc)
directional selection
type of natural selection where one extreme phenotype is favoured, causing the average trait in a population to shift in one direction over time.
disruptive selection
type of natural selection where 2 or more extreme phenotypes are favoured. 2 or more different habitats
founder effect
occurs when a few individuals form a new colony and their collective genes represent only a fraction of the original gene pool
gene flow
the movement of alleles between populations
- individuals migrate from one population to another
genetic drift
occurs when populations are drastically reduced in size.
heterozygote advantage
only alleles that are expressed are subject to natural selection. the heterozygote is a potential protector of recessive alleles
mutation
genetic changes that are the only source of new variation in a population
natural selection
process that allows some individuals with an advantage over others to survive and produce more offspring. it acts on phenotypes and results in adaptation
nonrandom mating
occurs when individuals are selective about choosing a mate.
stabilizing selection
extreme phenotypes are selected against. a constant environment
biosphere
the portion of the earth where living organisms exist
community
consists of all the various populations at a particular location
ecology
The study of the interactions of organisms with each other and with their physical environment
ecosystem
encompasses a community of populations, as well as the nonliving environment
extrinsic factors
External environmental influences.
Predation
Climate/weather
Food/water availability
Habitat loss
Natural disasters
intrinsic factors
Internal, biological factors affecting a population.
Reproductive rate
Genetic diversity
Intraspecific competition
Social behavior
Age structure
population (N)
all organisms of the same species interacting with the environment in a particular
population density (Dp)
the number of individuals of a species per unit area or volume
biotic potential
the highest possible per capita rate of increase for a population
carrying capacity
the number of individuals of a species that a given environment can support
exponential growth
π Exponential Growth (Ecology)
A rapid population increase under ideal, unlimited conditions.
J-shaped curve
Resources are abundant
Birth rate > death rate
No limiting factors (temporarily)
growth rate (gr)
describes how quickly a population is increasing or decreasing
lag phase
growth is slow because of a small population
logistic growth
The amount of environmental resistance increases
as the population grows. This eventually causes
population growth to level off, resulting in logistic
growth, an S-shaped curve with four phases:
1. Lag phase
2. exponential growth phasee
3. logistic growth phase
4. stable equilibrium phase
per capita growth rate (cgr)
represents the change in population relative to the initial population size
population change (οN)
βπ = πππ‘ππππ‘π¦ + ππππππππ‘πππ β ππππ‘ππππ‘π¦ + πππππππ‘πππ
stable equilibrium
Little growth occurs because births
and deaths are equal.
abiotic
non living factors like weather and environmental change
Batesian mimicry
a prey that is not harmful mimics another species that has a successful antipredator defence
biotic
living factors. competition, predation, parasitism, etc.
commensalism
One species benefits; the other is neither benefited nor harmed. One species may provide a home or transportation for the other.
competition
Competition occurs when members of two species
try to use the same limited resource.
competitive exclusion
No two species can occupy the same ecological niche at the same time if resources are limited.
* One species will eventually out-compete the other.
density-dependent
- Effects depend on the size of the population
- Biotic factors (competition, predation, parasitism, etc.)
density-independent
- Effects are the same for all sizes of populations
- Abiotic factors (weather, natural disasters, etc.)
ecological niche
An ecological niche is the role a species plays in the
community.
host
A parasite derives nourishment from another
organism called the host.
K-strategist
equilibrium pattern
Usually, K-strategists exhibit the following traits:
* Large in size
* Slow to mature
* Long life span
* Few large offspring
* Parental care
* Populations tend remain at carrying capacity
* Specialists (more vulnerable to extinction)
Examples include birds and mammals.
MΓΌllerian mimicry
species resemble each other and share the same successful defences
mutualism
Both species benefit, although the degree of
benefit may not be equal.
parasitism
A parasite derives nourishment from another
organism called the host. The parasite benefits,
and the host is harmed.
predation
Predation occurs when one organism, the
predator, feeds on another, the prey.
resource partitioning
Feeding niches may be divided between species.
* Decreases interspecific competition, thereby allowing
survival via occupancy of different niches.
r-strategist
opportunistic pattern
Usually, r-strategists exhibit the following traits:
* Small in size
* Mature early
* Short life span
* Many small offspring
* Little or no parental care
* Populations tend to grow quickly
* Generalists (not as vulnerable to extinction)
Examples include weeds and insects.
symbiosis
Symbiosis refers to close interactions between members of different species.
climax-pattern model
particular areas will always lead to specific climax communities.
* Based on the fact that climate helps determine whether a desert, a grassland, or a forest results.
facilitation model
each community prepares the environment for the next.
* Grasses are necessary before shrubs, and then shrubs before trees. It is a sequential process.
inhibition model
the colonizing species stays until they die or are damaged.
* The colonizing species makes the area less hospitable for new successive species.
pioneer species
first to begin process of succession
primary succession
Primary Succession: Establishment of a plant community in a newly formed area lacking soil.
* This could be due to a major disturbance, such as a
volcanic eruption or glacial retreat
secondary succession
Secondary Succession: Return of a community to its natural vegetation following a disturbance.
tolerance model
different plant types can colonize at the same time.
* Random chance determines which arrives first.
