Ecology Shapes Evolution

The study of interaction between an organism

and its environment and to one another.

• Defined as the change that occurs in the characteristics of

the living things over time.

– It may be change in the form and behavior of organisms

between generations

– It may be genetic changes in a population of organisms over

time.

• Evolutionary solution

• a genetically determined characteristics that improves

an organism’s ability to survive and reproduce in a

particular environment.• Behavioral, morphological or physiological.

• Ecology for the most part ignores evolution because

organisms are treated as constants," said David Reznick,

an evolutionary biologist at the University of California

• the general assumption is that ecological interactions

happen on such a short time scale in comparison to

evolution that evolution can be ignored

• refers to diversity in gene frequencies.

• is a term used to describe the variation in the DNA

sequence in each of our genomes

The basic evolutionary unit is

Population.

• Population

– A group of individuals of the same species that live in the same

area and interbreed.

• Gene pool– Consist of all the genes in all the individuals making up a

population.

• Mutations

• Gene flow (migration)

• Genetic Drift

• Natural Selection

• Sex

• A heritable change in the kind, structure, sequence or

number of the component parts of DNA.

– Produce new alleles and new genes.

• Original source of genetic variation that serves as raw

material for evolution.

• Are random

• Effects depends upon on how it changes the structure, function

or behavior of the individual.

– may be beneficial, neutral, or harmful to the individuals that inherit

them.

Chemicals, radiation, copying errors

• Mutations do not try to supply what the organism

needs.

– These mutations are not likely to account for a change in allele

frequency.

– These good mutations bring new genetic information into the

genetic pool.

• The movement of alleles between

populations as a result of movement of

individuals from one population to

another.

• A change in allele frequency that can occur

when mating with members from another

population occurs.

• Tends to reduce differences between

populations over time

• Chance events that cause allele frequencies to fluctuate

unpredictably from one generation to the next.

• Chance determine reproductive success.

• Tends to reduce genetic variation

If there is a drastic change (disease or natural catastrophe) in the

survival of a large population, there is little change in the frequency of

that population's alleles. In a smaller population, drastic change can

result in loss of an entire allele.

Genetic Drift

Genetic Drift: Bottleneck effect

• The change in allele frequency in a population due to

chance following a sharp reduction in the population size.

• When a small portion of a population migrates to another area,

starting a new population.

• The allele frequencies in their gene pool may be different than the

original population.

Genetic Drift: Founder effect

Natural Selection

• is the process by which individual organisms with

favorable traits are more likely to survive and reproduce.

Natural Selection

• traits determine reproductive success;

• Alleles that confer “success” are more likely to be passed on to future

generations and will increase their % relative to other alleles over time.

Technical term for “success” is differential reproductive success

• Natural selection is the primary mechanism of

adaptive evolution• Accumulates and maintains favorable genotypes in a

population

• Natural selection increases the frequencies of

certain genotypes, fitting organisms to their

environment over generations

Sexual Selection

• a form of natural selection in which individuals with certain

traits are more likely than other individuals to obtain

mates.• Is a direct competition among individuals of one sex for mates of the

opposite sex

• Sexual Dimorphism

– Distinction in the appearance between male and female

Intersexual selection

Intrasexual selection

2 Processes Involved In Evolution

• Adaptation

– traits that confer an advantage to those individuals who leave

more offspring

• Speciation

– The smallest independently evolving unit.

What is a Species?

A species is a group of individuals capable of interbreeding to

produce fertile offspring.

This is the biological

species concept. Like all

attempts to define a

species, it has a problem.

Biological species concept

• defined as a group of individuals that actually or potentially interbreed in nature.

• Focus on similar characteristics AND the ability of organisms to interbreed in

nature and produce viable, fertile offspring

• ADVANTAGE:

• It is widely used by scientists

• DISADVANTAGE:

• Can’t be applied for species the reproduce asexually

• Uncertain for populations that are physically separated and don’t have the

opportunity to breed naturally

• Can’t be applied to fossil species, which are no longer reproducing

Morphological Species Concept

• Focus on the morphology of an organism.

• It refers to the body size, shape and other structural features.

• Advantage:

• This can be applied to asexual organisms and fossils

• Does not require information on possible interbreeding.

• Disadvantage

• Too much variation within a species

• Approach relies on subjective criteria, and researchers may disagree on which features

distinguish a species.

Speciation

http://scienceblogs.com/evolvingthoughts/2007/03/11/basic-concepts-allopatry-and-s/

The key to speciation is the evolution of

genetic differences between incipient

species.

Reduction to gene flow plays a critical

role in speciation.

Allopatric Speciation: The Great Divide

Speciation by geographic isolation

Two models of allopatric speciation

• Dispersal model: colonization of remote islands by mainland organism

Vicariance may be due to a variety of factors:

• Changes in courses of rivers

• Mountain-building events

• Volcanism

•Environmental changes

Two models of allopatric speciation

• Vicariance model

Allopatric Speciation: A change in the environment

Two species of ground squirrel are believed to have descended from a

common ancestral population that was separated by formation of the Grand

Canyon.

Harris’ antelope squirrel White-tailed antelope squirrel

Sympatric Speciation

Does not require large scale geographic distance

to reduce gene flow between parts of population.

• A new species arises within the same

geographic area as its parents.

• Occur when mating and resulting gene flow

between populations are reduced by factors

such as polyploidy, habitat differentiation, and

sexual selection.

Sympatric Speciation

• Industrial Melanism

Sympatric Speciation

Some key insights:

-Mating occurs on the host plant

-The adult female selects the host

-Host selection is under genetic control

-Reproductive isolation by different factors

Domestication

Extinction

Causes of Extinction: Habitat Alteration

Hunting

Predator control

Mutation

Immigration

Individual Selection

Individual Selection VS Group Selection

ALTRUISM

• may be explained by the

natural instinct to improve

the chances of passing on

one's genes.

• Behavior that benefits others

at a personal cost to the

behaving individual.

Evolution of Evolution: Mimicry