evolution test

two goals for all living things

survive and pro create

Process of Evolution

VARIATION, SELECTION,ADAPTION

VARIATION

Variations in a population exist because of mutation and recombination of genes

SELECTION

Some heritable variations allow organisms to survive and reproduce more (in evolutionary terms, fitness)

ADAPTION

1. Process by which an organism becomes better fit to its environment due to selection

2. Characteristic of an organism that makes it more fit in its environment

What is an adaptation

A characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment

Adaptations can be

Structural, Behavioural, Physiological

Structural - Adaptations

physical characteristics of an organism such as the
fur on a bear

Behavioural - Adaptations

Behaviours organisms do to thrive. For example,
migration and mating calls (birds)

Physiological - Adaptations

internal systematic responses to external stimuli
that keep organisms in balance (homeostasis)

Mimicry

Harmless species physically resemble a harmful species. Predators avoid the harmless species as much as they do the harmful one.

Camouflage

a type of structural adaptation, that allows organisms to blend in with its environment and avoid being eaten by predators.

Lamarck’s principle

Use and disuse, The inheritance of acquired characteristics,

Use and disuse - Lamarck’s principle

Body parts that are used become larger and stronger.

Body parts that are not used deteriorate.

The inheritance of acquired characteristics - Lamarck’s principle

Individuals can pass characteristics they had acquired during their lives, to their offspring.

Darwin Came to believe

● That species survived through a process called natural selection

● Species that were able to adapt to meet the changing needs of their natural habitat survived and reproduced, while those that failed to evolve and reproduce died off

Natural selection

the way in which the environment, or nature, favours the reproductive success of certain individuals over others.

evolutionary fitness

How well a species is able to reproduce in its environment

Homologous structures

similar structures that but different functions

• Similar because they were inherited from a common ancestor

Analogous Structures

different structuea, simlar functions

Vestigial features

features that no longer serve the function they do in similar species

DNA Sequencing

Comparing nucleotide arrangements in DNA across different organisms and looking for similarities to suggest common ancestry.

Fossil Record

Fossil records show physical evidence of organisms from the past and reveal how species change over time.

Artificial Selection

The process of selection under human direction

Gene Pool

all the genes of all the individuals in a population.

Allele

a different form of the same gene (brown hair vs. blond hair)

5 common factors that cause evolutionary change

1. Gene flow (migration)

2. Mutation

3. Non-random mating

4. Natural Selection

5. Genetic Drift

Gene Flow (Migration)

may change allele frequencies in either one or both populations through a “flow” of genes

Example

• Hamadryas baboons in Saudi Arabia.

- at some point in their lives, female Hamadryas

baboons leave their birth group and migrate to a different one.

- this promotes gene flow between different groups,

helping all populations maintain healthy and diverse gene pools.

Mutation

•Change that occurs in the DNA of an individual

•Randomly introduces new alleles into a population

Effect: Mutation changes allele frequencies

Non-random mating

•Mating among individuals on the basis of mate selection for a particular phenotype (what they look like) or due to inbreeding.

Effect: Non-random mating increases the proportion of homozygous individuals in a population but does not affect the frequencies of the alleles.

Natural Selection

• Result of the environment selecting for individuals in a population with certain traits that make them better suited to survive and reproduce than others in the population.

Effect: Over many generations, frequencies of alleles of many different genes may change, resulting in significant changes in the characteristics of a population.

Genetic drift

• Changes to allele frequency as a result of chance

• Genetic drift can cause big losses of genetic variation for small populations

• Most natural populations are large enough that effects of genetic drift are small

• Two situations can lead to significant genetic drift

BOTTLENECK EFFECT

• changes in gene distribution that result from a rapid decrease in population size

● starvation, disease, human activities (hunting) and natural disasters (typhoon/tsunami/forest fire) can quickly reduce size of a larger population

● Bottleneck effect is often seen in species driven to the edge of extinction

FOUNDER EFFECT

• Founder Effect: a change in the gene pool that occurs when a few individuals start a new isolated population.

• New population is formed by only a few individuals, or founders

• The founder effect occurs frequently on islands

Directional selection

selection that favours individuals with a more extreme version of the characteristic.

○ This results in a shift away from the average condition

○ Common in artificial breeding

Stabilizing selection

occurs when the average phenotype within a population is favoured by the environment. Selection is against individuals exhibiting traits that deviate from the current population average

Disruptive selection

favours individuals with variations at opposite extremes

of a trait over individuals with intermediate variations

Sexual Selection

● the favouring of any trait that enhances the mating success of an individual.

○ often leads to the males and females of a species evolving appearances and behaviours that are very different from each other.

Genetic drift

the random shifting of the genetic makeup of the next generation; these changes are much more pronounced in small populations

Genetic bottlenecks

result in a loss in genetic diversity following an extreme reduction in the size of a population

Founder effect

occurs when a small number of individuals establish a new

population

Microevolution

changes that occur within species

Speciation

the formation of a new species

Pre-zygotic Barriers

● differences in breeding season, physical or behavioural traits, habitat preferences, or the incompatibility of gametes.

● Prevents interspecies mating and fertilization

Prezygotic Isolation - Ecological Isolation

similar species become reproductively isolated because they adapted to different habitat in the same location

Prezygotic Isolation - Temporal Isolation

species have different breeding seasons (time)

Prezygotic Isolation - Behavioural Isolation

different signals or rituals for attracting mates

Prezygotic Isolation - Mechanical Isolation

reproductive structures are physically incompatible

Prezygotic Isolation - Gamete Isolation

sperm and egg of different species are unable to recognize each other by their molecular markers

Post-zygotic Barriers

● can prevent a fertilized egg from growing into a viable and reproducing adult

Postzygotic Isolation - Zygote mortality

zygotes do not develop to maturity

Postzygotic Isolation - Hybrid inviability

some hybrid dies early in development

Postzygotic Isolation - Hybrid infertility

Hybrid offspring survive but are infertile.

Modes of Speciation

● New species are created when 2 populations are reproductively isolated

● These populations can be isolated in two ways:

○ Allopatric speciation

○ Sympatric speciation

Allopatric Speciation

When 2 populations become geographicall separated, mutations occur until the populations are reproductively isolated

Sympatric Speciation

o Populations in same geographical location split into separate gene pools due to genetic polymorphism (2 or more different phenotypes)

o Often due to disruptive selection