Or Bio Exam 1 -(Pt. 4 SPECIATION)

What is a speciation?

When one species splits into two or more new species that can’t interbreed.

What is a microevolution?

• Microevolution: Small changes in a population over time (allele frequencies, traits). Speciation can possibly happen over time.

What is a macroevolution?

• Macroevolution: Large changes over long periods; speciation has happened (new species form).

What is a Biological species concept? BSC?

BSC states that a species is a group of organisms that can naturally mate and have healthy, fertile babies, and can’t do this with other groups.

What are the limitations of BSC?

• Doesn’t work for asexual organisms (bacteria, some plants).

• Hard to apply to fossils—can’t test if they interbred.

• Some species can hybridize (e.g., wolves and dogs) but are still considered separate.

Reproductively isolated?

Two same looking birds can’t reproduce since they were two different species.

Definition: What are prezygotic and postzygotic barriers?

• Prezygotic barriers: Prevent mating or fertilization before a zygote forms.

• Postzygotic barriers: Occur after fertilization, stopping the hybrid from surviving or reproducing.

What are the prezygotic barriers?

Prezygotic (before fertilization):

• Temporal – breed at different times

• Behavioral – different mating behaviors

• Habitat – live in different places

• Mechanical – physical differences prevent mating

• Gametic – sperm and egg incompatible

What are the postzygotic barriers?

Postzygotic (after fertilization):

• Hybrid inviability – embryo doesn’t develop

• Hybrid sterility – offspring are sterile

  (sterile: can’t produce offspring)

• Hybrid breakdown – offspring of hybrids are weak/infertile

What is a Morphological Species Concept?

It’s an other definition of species, defining species by it’s physical trait.

It’s an other definition of species, defining species by it’s unique role or niche, how it interacts with environment and organisms.

How can speciation occur?

2 ways, Allopatric speciation and sympatric speciation. Both speciation’s gene flow got disrupted.

How does allopatric speciation occur?

• Two populations of the same species are geographically separated (mountains, rivers, islands).

• Mechanisms of evolution like natural selection, mutation, and genetic drift cause genetic divergence.

• Over time, the populations develop reproductive isolation.

• Result: two different species.

How does sympatric speciation occur?

• Speciation occurs without geographic separation.

• Can happen through genetic changes:

  • Autopolyploidy: chromosome duplication in one species.

  • Allopolyploidy: hybridization between two species with combined chromosomes.

• These changes cause reproductive isolation, forming a new species in the same area.

what is a Polyploidy

Extra sets of chromosomes from cell division mistakes; more common in plants than animals.

Differences between Autopolyploidy and Allopolyploidy?

• Autopolyploidy: Chromosome duplication within a single species → can’t mate with original population → new species forms.

EX: Potatoes

• Allopolyploidy: Hybridization between two different species → combined chromosomes → new species forms.

EX: Wheat

Compare allopatric & sympatric speciation.

Allopatric = geographic separation.

Sympatric = no physical barrier.

Example of Allopatric vs Sympatric speciation?

Allopatric speciation: Galapagos finches

Sympatric speciation: Anolis lizard

hat is a hybrid zone?

Literally hybrid zone, 2 species boom boom = hybrid.

What is punctuated equilibrium?

Species stay the same for long periods and then rapidly change in short time.

What is gradualism?

evolution that is slow, but keep changing.

What is an Adaptive radiation?

One species rapidly evolves into many new species to fill different ecological niches.

Ecological niches: The role or “job” of a species in its environment—where it lives and what it does.

When does adaptive radiation happen? Example?

When a species moves to a new area or after mass extinctions open up space.

Example: Darwin’s finches.