Biology: 4-1 Notes

Evolution

Change in one type of organism over time

Evolution

Process in which all organisms have changed over time

What is 1 of the main principles of the theory of evolution?

All organisms share a common descent from unicellular ancestors (bacteria)

What is another 1 of the main principles of the theory of evolution?

All organisms have descended over time into many forms with different traits and adaptations

What is another 1 of the main principles of the theory of evolution?

The mechanism that causes organisms to change over time is "natural selection"

Speciation

The evolution of a new species

Species

Organisms that can reproduce AND create fertile offspring

Hybrid animals

Hybrid animals are not fertile and cannot breed (example: a Liger)

What's the 1st step of speciation?

Genetic Change-Changes to the genetic codes (genotype) within a species; and possibly its traits (phenotype)

What is 1 type of genetic change?

Mutations-Random changes to DNA/the genetic code

What is another type of genetic change?

Recombination-Random genetic mixing caused by meiosis and sexual fertilization

What's the 2nd step of speciation?

Variations-Different phenotypes between organisms in a population that may help it survive

What's the 3rd step of speciation?

Adaptations-An inherited variation that increases an organism's chance of survival

What are 2 types of adaptations?

Behavioral adaptations and physical adaptations

What's the 4th step of speciation?

Speciation- the evolution of a new and genetically unique species

NOTE: At some point in these steps "reproductive isolation" must occur.

Reproductive isolation

When barriers exist that cause members of two populations to be unable to interbreed and produce fertile young

-Isolation over time causes their genetic codes to change to the point in which they become a new species

Sympatric Speciation (1st main type of speciation)

The isolation occurs inside the habitat of the parent population

Allopatric Speciation (2nd main type of speciation)

The isolation of a small group outside the habitat of its parent population

What are the 2 main types of reproductive isolation?

Prezygotic and postzygotic

Prezygotic barriers

Barriers that don't allow organisms to attempt to make a zygote (the 3 isolations)

What are the 3 Prezygotic barriers?

Geographic isolation, Behavioral isolation, and Temporal isolation

Geographic Isolation

Allopatric speciation where two populations are separated by land barriers and thus can no longer reproduce

Examples= a species separated by deserts, mountains, ocean, canyons, etc.

Behavioral Isolation

Sympatric speciation where two populations of species are able to reproduce but do not because of different mating rituals

Examples= making nests differently, changing mating calls or dances, mating on different surfaces

Temporal Isolation

Sympatric speciation where two or more species do not reproduce at the same time so they can't interbreed

Examples= flowers opening at different times or animals mating at different times/seasons

Postzygotic barriers

Genetic barriers that don't allow the formation of a zygote

What are 2 postzygotic barriers?

Genetic incompatibility-DNA can't combine effectively

Hybrid sterility