SPECIATIONCh. 16-3 pp. 326-330

Warm up 2/25: • Define: Homologous Structures, Analogous Structures and Vestigial Organs/Structures.

•Give 1 example of each•What is the main difference between a homologous structures and vestigial Structures.

Forming a new species

Speciation: forming a new species Species: a group of organisms that

can mate and produce fertile offspring 1. same number of chromosomes 2. similar morphology (body structure)

Species Types

Morphological Species – Defined using similar characteristics.

Biological Species – A species can reproduce and have fertile offspring. A group of organism that can successfully

interbreed. Cannot breed fertile offspring with other

species.

Disruptive Selection

Divergent evolution that most likely results in two new species

Mechanisms

Allopatric speciation caused by geographic isolation (physical separation of organisms)

Mechanisms Cont.

Sympatric Speciation due to reproductive isolation (barriers to successful breeding) Prezygotic: before fertilization (i.e breeding

times or home range) Postzygotic: after fertilization- infertile offspring (chromosome # doesn’t add up)

Liger – Tiger and Lion produce an infertile offspring

Rates of Speciation

Gradualism: slow divergence Punctuated equilibrium: sudden

shift in form (irregular)

Homework: Tri-fold Vocab Due Tuesday 2/26 Genetic Drift Biological Species

Concept Allopatric Speciation Sympatric

Speciation

Prezygotic Isolation Postzygotic Isolation Gradualism Punctuated

Equilibrium Speciation

Homework: Due Wednesday 2/27Read p326-330 Do p 330 # 1-7Study Guide & Raft Due ThursdayExam Friday: Intervention this week.