Evolution

What is Temporal Isolation?

two populations are unable to exchange alleles because they are available to exchange alleles at different times of the year or day

What is evolution?

the process in which significant changes in the inheritable traits of a species occur over time.

Why is their evolution?

Adapt to **environmental changes** in order for species to **survive and reproduce.**

What are the two perspectives?

Religion and Science

Who is Charles Darwin?

Called the *Father of Evolution.* Proposed a mechanism for evolution, natural selection

What did darwin do?

Darwin went on a 5-year trip around the world on the ship, the HMS Beagle. Wrote a book, “*Origin of the Species*” (1859)

What are the peices of evidence for evolution?

Fossils, Biogeography, comparative anatomy, Comparative Embryology, Comparative Biochemistry,

What is biogeography?

**Biogeography** the scientific study of the geographic distribution of organisms based on both living species and fossils.

How does biogeography prove evolution?

Biogeography can be used to show that organisms that live in similar environments tend to evolve in similar ways, even if they are only distantly related.

What is comparative anatomy?

Comparative anatomy involves studying and comparing the structure of different organs. Two organisms are related if their organs have a similar internal structure, even if they are shaped differently.

What are Homologous Structures?

Are similar in structure and share a common origin (i.e. ancestor) but may be adapted to perform **different functions**.

What are Analogous Structures?

Are shared by **unrelated organisms** and have evolved to perform the same function.

What are Vestigial Features?

organs found in some living things, that do not perform any functions. They simply show an evolutionary relationship with other living things.

What is natrual selection?

Organisms that are best adapted to an environment *survive* and *reproduce* more than others

What is Darwin’s Theory of Natural Selection?

Overproduction, Variation, Competition and Selection

What is overproduction?

Each species produces more offspring than can survive

What is Variation?

Each individual has a unique combination of inherited traits. The more variation within a species, the more likely it will survive

What is competition?

* Individuals COMPETE for limited resources:
* Food, water, space, mates

Natural selection occurs through “Survival of the fittest”

What does survival of the fittest mean?

the ability to survive and reproduce

What is selection?

The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring (phenotype)

What is **Sexual Selection?**

the selection of any trait that influences the mating success of an individual. traits that are favoured tend to be sexually dimorphic

What is **Intersexual Selection?**

female choice is based on colouration, courtship displays, songs, etc.

What is Intrasexual Selection?

male/male competition, e.g. strength to fight other males or defend territory

What is Artificial Selection?

domestication of plants and animals = changing members of a species to suit human needs

What are selective pressures?

environmental **factors or influences which may lessen reproduction** in a species’ population

Examples of selective pressures?

Competition, predation, land clearance, Pollutants, diseases and illnesses, climate change and parasitism.

what are the Factors that Cause Evolution

Mutations, Gene flow (migration), Non-random mating, Genetic drift (bottleneck and founder effect), Natural Selection

what are Mutations

Mutations are changes in the DNA of an individual but if they are heritable they could impact an entire population’s gene pool.

What is gene flow?

Net movement of alleles from one population to another due to the migration of individuals.

What is non-random mating?

Mating among individuals on the basis of mate selection for a **preferred phenotype** or due to **inbreeding.**

What is genetic drift?

the change in allele frequencies due to **chance** events in a population

What is the founder effect?

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

What is the bottle neck effect?

Disasters such as earthquakes, floods, droughts and fires can drastically reduce the population which also reduces the gene pool and decreases variation in population.

What are the 3 types of natural selection?

Stabilizing selection, Directional selection and Disruptive selection

What is stabilising selection?

most common form of selection, the extreme values for a trait are selected against, over time, the population mean stays the same and the range decreases

What is  Directional Selection?

selection favours one of the extremes, peak moves in one direction

What is   Disruptive Selection?

selection favours both of the extremes in a population, two peaks

What is Divergent Evolution?

two or more species evolving increasingly different traits as a result of different selective pressures or genetic drift

What is Convergent Evolution?

two unrelated species being subjected to similar selective pressures which result in similar phenotypes

What is Speciation?

two populations become completely isolated and no longer exchange alleles, they are said to have formed separate species.

What is Allopatric Speciation?

two populations are geographically isolated prior to becoming separate species e.g. fish separated by a dam

what is Sympatric Speciation?

two populations remain in physical contact with each other but still stop exchanging alleles

What are Reproductive Isolating Mechanisms?

In order for one population to become very different from another, they must be reproductively isolated. This means that there will no longer be a free exchange of alleles between two populations.

What are Prezygotic mechanisms?

prevent mating or fertilization.

What are Postzygotic mechanisms?

prevent the development of fertile offspring.

What are the Prezygotic Mechanisms?

Ecological Isolation, Temporal Isolation, Behavioural Isolation, Mechanical Isolation, Gametic Isolation

What is Ecological Isolation?

two populations are in different geographical places or in different places within the same ecosystem

what is Behavioural Isolation?

two populations do not respond to each others mating rituals

What is Mechanical Isolation?

a physical barrier that prevents fertilization or mating

What is Gametic Isolation?

two populations exchange gametes but chemical markers prevent the eggs from being fertilized by the ‘wrong’ sperm

What are the Postzygotic Mechanisms?

.  **Zygotic** mortality, **Hybrid** Inviability, Hybrid Infertility

What is **Zygotic** mortality?

even though zygote is created, it fails to develop to **maturity**

What is **Hybrid** Inviability?

even though the hybrid is **born**, it does not live long or is **not healthy**

What is  Hybrid Infertility?

even though hybrid is healthy and vigorous, it is not able to reproduce