Lecture 14: Macroevolution & Phylogenies

KRAMER - UH

macroevolution

evolutionary changes that result in new species

speciation

the process by which one ancestral species splits into two or more unique species

3 ways to classify an organism as a unique species

1. Morphological Features

2. Biological (Reproductive isolation)

3. Molecular Features

Morphological species concept

classification based on physical traits (shape, size and form)

species

a population that can interbreed in their natural habitat and share morphological and genetic/molecular similarities

convergent evolution

Two different species from different lineages show similar characteristics because they occupy similar environments

analogy

similar environmental pressures resulted in similar features evolving separately from each other

Reproductive Isolation

set of mechanisms that prevent different species from interbreeding and producing viable offspring

Prezygotic Barriers

Block Fertilization from occurring; factors that impede members of two species from interbreeding

Habitat isolation

members of different species never come in contact with each other when breeding

Temporal isolation

species reproduce at different times of the year.

Behavioral isolation

mating behavior differs

Mechanical isolation

morphological features are incompatible

Gametic Isolation

two species attempt to interbreed but gametes fail in successful fertilization

Postzygotic Barriers

Developmental errors or post birth problems that decrease the chance of surviving long enough to reproduce

Hybrid inviability

egg from one species is fertilized by the sperm of another, but the fertilized egg may not develop past embryonic stages

Hybrid sterility

an interspecies hybrid survives but it is sterile

Hybrid breakdown

the F1 interspecies is viable and fertile, but succeeding generations become increasingly inviable

Allopatric Speciation

population forms a new species while geographically isolated from its parent population

Sympatric Speciation

subset of a population forms a new species without geographic separation

adaptive Radiation

a single ancestral species gives rise to a wide array of descendant species.

Binomial Nomenclature

A Latinized two- name system used to classify organisms by their genus and species

Taxonomic group (from broad to narrow)

Domain (largest)

Kingdom

Phylum

Class

Order

Family

Genus

Species (smallest)

Phylogeny

evolutionary history of a species or group of species

Phylogenetic tree

a diagram that describes the evolutionary relationships among various species, based on the information available

Anagenesis

single species evolves into a different species

Cladogenesis

a species diverges into two or more species

Paraphyletic group

Contains a common ancestor and some, but not all, of its descendants

Monophyletic group

Includes an ancestral species and all of its descendants

Polyphyletic group

Consists of members of several evolutionary lines and without the common ancestor