BIO 337 - Exam 2

Natural Selection *on individual level

process where characteristics that give an advantage are preserved. (Some individuals, because of heritable traits have a higher chance of surviving and reproducing.)

Adaptation

Response of population to environmental pressure on individual variation

Alleles

Different forms of a gene (dominant or recessive)

Evolution

The change in gene frequency within a population over time.

Mendel

Father of genetics

Darwin

Father of evolution; wrote book of origin species

Wallace

Natural selection evolution; wrote book island life

Hardy-weinberg equilibrium model

In absence of evolutionary forces, random mating will result in constant allele frequency with a population.

• No gene flow

• No natural selection

• No mutation

• No genetic drift

• No non random mating

Stabilizing selection

Acts against extreme phenotypes

Directional selection

favors and extreme phenotype over other phenotypes.

Disruption selection

Favors 2 or more extreme phenotypes.

Adaptive change

Not in individuals but in populations.

Genetic drift

Fluctuations in gene frequency such that genes of offspring are not perfectly representative of genes in the parental generation - especially prominent in small populations.

Island population

Less genetically diverse than mainland population because of the founder effect.

Bottleneck effect

a type of genetic drift that occurs when a dramatic, random event sharply reduces the size of a population, leaving behind a small, non-representative group of survivors with a severely limited gene pool.

Heritability

H²= VG (genotype) /VP (phenotype) + VE (environment)

Population

A group of individuals of the same species living in the same place at the same time.

Density

# of individuals per unit of area. (How crowded is the area?)

Distribution

Range that a species occurs with in. (ex. lions)

Abundance

Total number of individuals in a area. (How many are there in total?)

Distribution patterns * Depends on scale *Nearly uniform, random, clumped

Small scale - distance <200m with little environmental change over the range

Large scale - Areas over which there is substantial environmental change

Random distribution

Individuals have equal chance of living anywhere within a area (ex. humpback whale, you see them randomly throughout their habitats.)

Regular distribution

Individuals are equally spaced. *due to limited resources, and being territorial they are regular distributed.

Clumped distribution

Individuals are found in clusters within the environment. *Individuals clump by resources

Species with small range..

Epicenter of population densities, most abundant closest to origin, then become less abundant as you move away from origin.

Species with large range…

Have many epicenters *find few, find many

Metapopulations

Group of populations that live in patches with some exchange of individuals between patches. *interactions between patches

Organism size and population density

Density decreases with size. Why? resources are limited

Extensive range, broad habitat tolerance, small local populations

Tiger, Falcon

Extensive range, large local populations, narrow habitat tolerance

Pigeon, Sucker

Restricted range, narrow habitat tolerance, low local population

Gorilla, panda

Emigration

Leaving

Immigration

Coming in

Birth rate (natality)

number of births per thousand, hundred, or individual per year

Death rate (mortality)

number of deaths per number of individuals per year.

Age structure

Distribution of number of individuals of each age class.

Sex ratio

number of males per number of females

Fecundity

number of eggs produced per female

Fertility

percentage of eggs that are fertile

Production

Actual number of offspring produced, by a population during a specific period of time.

Recruitment

number of new individuals that enter each age class (including immigration)

Life table

Method of tracking survivorship and deaths in a population.

Cohort

Group born at the same time

Cohort lift table

Snapshot of survival in a population over a short time

Age distribution

Proportion of individuals of different ages within a population. (Ex. juveniles, breeding)

Static life table

Snapshot of survival in a population over a short time.

Survivorship curves

Plot number of survivors per 1000 births against age

I = High initial, steep death rate as age limit is reached

II = Constant death rate

III = High initial morality, but those who survive live long

Fecundity schedule

Tabulation of birthrates for females of different ages within the same population.

Net reproductive output = Ro

• Ro > 1 = population increase

• Ro < 1 = population decrease

• Ro = 1 = no change

λ

Geometric rate of increase (Eq. λ = Nt+1/Nt)

N=# of individuals

t=time

Nt=origin timestamp

Dispersal

Moving from birth spot - can be influenced by climate, food sources, and competition

Geometric population growth *need to know all numbers

Growth of a population with pulse reproduction (insects, plants)

Exponential growth *bactera

Growth not limited by the environment *basically unchecked by the environment until their not

r *can be negative

intrinsic rate of increase

*populations only increase and decrease in 2 ways

1. birth rate vs. death rate

2. immigration vs. emigration rate

Logistic population growth

Growth is limited by the environment

Density dependent factors *compensatory manner

Biotic factors, predation disease, limited food resources

Density independent factors *additive manner

Abiotic factors, cold snap, hurricane, earthquake, fire *indep of the population, not their fault this is happening

Primary sex ratio

Sex ratio at fertilization 50:50

Secondary sex ratio

Sex ratio at birth or hatching, may show signs of sex specific mortality (49:50)

Tertiary sex ratio

Sex ratio of juveniles, predicts ratios moving into breeding class, sex specific mortality may become important.

Quaternary sex ratio

Sex ratio of the adult population, many times skewed because of sex specific mortality.

Additive mortality

Individual killed by a force (hunting, disease, catastrophe) are in addition to those that would suffer mortality regardless of whether or not the force is present.

Ex. disease enters kills additional 100; a total of 200 die

Compensatory mortality

Individual killed by a force are excess and would suffer mortality regardless of whether or not the force is present *not important in decreasing our population

Ex. disease enters and only 100 total die, mortality from disease is compensatory.

Hunting mortality *acts in compensatory manner on population with high annual natural mortality

a = m + n - mn

a = crude mortality

m = hunting mortality

n = natural mortality

Model *model is only as good as the data you put in it

Any physical or abstract representative of the structure and function of a real system.

Thomas Malthus (1766-1834)

First observed that lack of food checks population, argued for regulation of human population.

Some say we are approaching our k (carrying capacity) 83 million added annually

Offspring number vs. size

Large number

not much energy into each, many offspring, hedge bet that 1 or 2 will survive. (Ex. Salmon)

Offspring number vs. size

Large size

More energy into each, each offspring has a greater chance of survival, but there are not as many.

(Ex. bald eagle)

Adult survival low

Reproduction begins at an earlier age, and greater energy is put into reproduction. (Ex. bunnies)

Adult survival high

More energy into survival, reproduction begins at a later age. (Ex. elephants)

r selection

Selection favoring higher population growth rate *not limited as much

(smaller, reproduce at younger age, high reproduction rate)

k selection

selection favoring more efficient utilization of resources. *limit

(larger, longer lived, lower rates of reproduction)

K

carrying capacity in population

Semelparity

Reproduction in one big event, lots of young eggs at once. (associated with r selection)

(Ex. insects)

Iteroparity

Repetitive reproduction, fewer young more than once. (associated with k selection)

Mutualism

+/+

Parasitism

+/ -

Competition

-/-

Commensalism

+/unaffected

Competition

The interaction among organisms within a community.

*competition can be over: light, food, space, water, nutrients, and reproductive rights

Infraspecific competition *can see in plants and animals

Competition within your species.

Effects population numbers, influences: births, deaths, and growth of individuals, density dependent.

3/2 self thinning law

Average plant volume increases about 1.5 units for each unit decrease in density.

*low density and high density stands will eventually conform to this.

Interspecific competition

Occur among species with similar environmental requirements or those that occupy similar niches.

2 or more species in a community compete for limited resources.

Interference

Fighting over resources *direct interaction

Exploitative

Consumption of similar resources *sucking all the resources in one spot

Pre-emptive

Monopolizing without fighting *no fighting, ex. geese - no room for anything else to come in

Niche (ecological)

Reflects the environmental requirements of an organism, how an organism “fits” into the environment. The total of an organisms use of biotic and abiotic resources.

Hutchinson’s definition of niche

n-dimensional hypervolume - all things for survival

n = number of environmental factors important for survival and reproduction by a species.

Niche overlap

Populations are lower, because of shared resources in the niche overlaps.

Ghost of competition past

Niches observed today, because theres been competition in the past.

Fundamental *larger

Physical conditions under which a species might exist minus competition/interactions.

Realized

The restricted conditions under which a species actually live with competition/interactions restricting occupation of a niche.

Competitive exclusion principle

2 species (inter comp) with similar needs competing for the same resources cannot co exist in the same place (niche). *someone will lose *can see in plants

Character displacement

A long term response to niche displacement

Gradual evolutionary separation of two species - morphological and physiological shifts

(Ex. darwin’s finches)

Allopatric

Separate

Symmpatric

Together