BIO

Morphological species concept

-Organisms of the same species share more similar characteristics with each other than those of different species because of a longer shared evolutionary history

-Do they look the same?

-Limitation: Large variation within species (dogs)

Genetic species concept

-Organisms of the same species share more similar DNA than those of different species because of a longer shared evolutionary history

-How similar is their DNA?

-Limitation: Large variation within species

Biological species concept

-Species are groups of organisms that can interbreed and produce fertile offspring and are reproductively isolated from other species

-Can they breed and create fertile offspring?

-Limitation: hybrid, extinct organisms, asexual species

What makes a species?

Members of the same species linked by shared evolutionary history via ability to exchange genetic information

Speciation

The process by which populations attain reproductive isolation and form a new species

Reproductive isolation

Biological barriers that impede members of different species from interbreeding and producing viable, fertile offspring

-2 types

Prezygotic barriers

Barriers that impede mating or hinder fertilization.

Mechanical isolation

Morphological differences, often in genitals, prevent mating

-Ducks

Temporal isolation

Species breed during different time of day, season, or year and thus can't mix gametes

-Hickory species

Behavioral isolation and mate recognition

Mating behavioral differences prevent mating, can't recognize mating signals

Post zygotic barrier

Prevents hybrid offspring of 2 species from developing into viable, fertile adult

Reduced hybrid viability

Hybrids either fail to develop or are very frail and unlikely to survive

Hybrid sterility

Hybrids may be sterile or have low fertility

-Mules

Allopatric speciation

Reproduction prevented by geographic isolation of a previously continuous population

-2 types

Vicariance

Population split by the formation of a geographic barrier

-Allopatric speciation occurs if populations accumulate enough genetic differences that they couldn't mate even if barrier removed

Dispersal

Distance as a result of movement to new areas results in reproductive isolation as populations no longer continuous

-Drosophila flies

Parapatric speciation

Geographically continuous populations over extremely vast distances experience divergence

-Individuals at either end of distribution functionally isolated from each other

-Ensatina eschscholtzii

Ring species

Continuous populations over large geographic areas form a ring that can interbreed except where the populations rejoin

Sympatric speciation

Speciation occurs in populations that live in the same geographic area

-Lake victoria cichlids

2 rates of speciation

1. Gradual model: species diverge steadily over time

2. Punctuated equilibrium: rapid bursts of speciation followed by relatively little change

Adaptive radiation

Periods of evolutionary change in which organisms form many new species with adaptations specialized to difference niches

-Often happens after mass extinctions of in newly colonized areas

Niche

The specific biotic and abiotic resources used by a species

Competitive exclusion

2 species will never be perfectly equally successful at utilizing a resource so more successful competitor will exclude the other from its niche

Resource partitioning

Similar species can coexist in an area if they use different sets of similar resources or the same resource at different times

Ecology

The study of the interactions between organisms and their biotic and abiotic environment

4 levels of ecology

1. Population ecology

2. Community ecology

3. Ecosystem ecology

4. Global ecology

Population

A group of individuals of the same species living in the same area

Population ecology

Studies population sizes and how and why they change over time

-California condors

Mark-recapture method (measuring population size)

Capture and mark an initial set of individuals, release to population, use proportion of re-caught individuals in second capture to estimate total population

(\# marked individuals in second capture/total individuals caught in second capture)=(# marked individuals in first capture/size of whole population)

Change in population size

Simple= births-deaths

Complicated= births + immigrants - deaths - emigrants

•Observed rates based on Population data:

•b = number of births/N

•d = number of deaths/N

r = b - d

Change in pop size=rN

Exponential growth

Number of individuals added each time interval increases as N increases in absence of factors limiting population growth

-Doesn't really happen in nature

Logistic growth model

Population growth slows as it approaches carrying capacity (maximum population size that a given environment can sustain)

Density dependent population regulation

birth and death rates vary as a function of population sizes

-Food, disease, predation

Density independent population regulation

birth and death rates do NOT change as a function of population size

-Drought, extreme storms

Survivorship

% of the population that survives to a give age

Survivorship curves

Plots of the proportion of individuals still alive in each age

-3 types

Survivorship curve type 1

High survival rate until later age

Survivorship curve type 2

a constant death rate over the organism's life span

Survivorship curve type 3

high death rates for the young and lower death rates for survivors

3 random mechanisms of evolution

1. mutation

2. genetic drift

3. gene flow

Genetic drift

a random change in allele frequencies from generation to generation

(relates to HW "large population size" requirement. Large populations less likely to experience genetic drift.)

Heterozygosity (H)

measures the probability of drawing 2 different alleles from the gene pool of a population (also called gene diversity)

H = 1 -(p^2 + q^2)

p = 0.5, q = 0.5 is the combination with the highest heterozygosity

bottleneck effect

occur when an environmental/human catastrophe kills a large percent of the population

-loses genetic diversity

-cheetahs

founder event

a new, smaller population of "founders" break-off from the original population

founder effect

occur IF the new population has lower genetic diversity than the original population

gene flow

introduction or removal of alleles from a population →change allele frequencies

(relates to HW requirement of "no migration")

mutation

a permanent, RANDOM change in the DNA sequence of an organism

•ultimate source of ALL variation that evolution acts on

community

a group of populations of different species that live close enough to one another to interact

intERspecific interactions

interactions between individuals of different species

• Defined by the effects the interaction has on the organisms involved

intRAspecfic interactions

interactions between members of the same species

Symbioses

when individuals of two species live in direct, intimate contact with each other for prolonged periods of time