Extinction. End of the line for a species Extinction. End of the line for a species. Mass extinctions are catastrophic events in which major groups are lost abruptly and simultaneously. Genetic disconnect Basis of life’s diversity, as brought about by adaptive shifts, branchings, and radiations. Rates and times of change varied within and between lineages. Genetic divergence Basis of the unity of life. The biochemical and molecular basis of inheritance extends from the origin of first cells through all subsequent lines of descent. Genetic persistence Macroevolutionary Processes Preserves or erodes species cohesion, depending on environmental pressures Natural selection Erodes species cohesion Genetic drift Preserves species cohesion Gene flow Stability or change in a species is the outcome of balances or imbalances among all of these processes, the effects of which are influenced by population size and by the prevailing environmental conditions. Original source of alleles Mutation Microevolutionary Processes Table 13.1  Summary of Processes and Patterns of Evolution Table 13.1 Page 218

Speciation Species- Individuals capable of successful interbreeding and producing fertile offspring. Speciation: process by which new species come into being Genetic divergence of reproductively isolated populations

Simplified diagram of genetic divergence time A time B time C time D daughter species parent species time

Reproductive Isolating Mechanisms Prezygotic Isolation Ecological Temporal Behavioral Gametic Mortality Postzygotic Isolation Zygotic Mortality Hybrid Inviability Hybrid Infertility

They interbreed anyway. Different species! Temporal isolation Mechanical isolation Behavioral isolation Ecological isolation They interbreed anyway. Gamete mortality Zygotes form, but... Hybrid inviability Do not post to Internet Hybrid sterility No offspring or weak offspring that die before reproducing

Types of Speciation Sympatric Speciation- Isolation within a population New species arises in the midst of the original population. Ex: Lake Victoria Cichlids Allopatric Speciation- Geographical isolation Thought to be most common means of speciation A geographic barrier, such as a river or a mountain range, causes the splitting of a population such that individuals of these now-separate populations can no longer interbreed. Ex: Grey Squirrels around the Grand Canyon Pioneering individuals may colonize a new habitat, such as an oceanic island. Ex: Hawaiian Honeycreeper

Do not post to Internet The shared ancestor of all of Hawaii’s honeycreepers probably looked like this house finch (Carprodacus) Akepa (Loxops coccineus) Akekee (L. caeruleirostris) Nihoa finch (Telespyza ultima) Palila (Loxioides bailleui) Maui parrotbill (Pseudonestor xanthrophrys) Alauahio (Paroreomyza montana) Kauai Amakihi (Hemignathus kauaiensis) Akiapolaau (H. munroi) Do not post to Internet Akohekohe (Palmeria doli) Apap (Himatione sanguinea) liwi (Vestiaria coccinea)

1 2 3 4 A few individuals of a species on the mainland reach isolated island 1. Speciation follows genetic divergence in a new habitat. 1 2 Later in time, a few individuals of the new species colonize nearby island 2. In this new habitat, speciation follows genetic divergence. 1 2 3 4 Speciation may also follow colonization of islands 3 and 4. And it may follow invasion of island by genetically different descendants of the ancestral species.

Patterns of Speciation Phylogeny- The evolutionary relationships among living, or extinct, organisms. Evolutionary Trees- Summarize information about the continuity of relationships among species; summarize phylogenies Branching in the tree represents speciation. Angling of a branch represents gradual change in a lineage= phyletic evolution. A straight line represents no change in a lineage. Branches ending before the present represents extinction. Adaptive radiation- Burst of divergence (branches) from a single lineage.

Patterns of Speciation

species 2 species 3 species 1 suspected branching a single lineage; ancestral stock branch point (time of genetic divergence, speciation under way)

Kingdom Genus Species Family Order Class Phylum Plantae Plantae Animalia Musca M. domestica Muscidae Diptera Insecta Anthropoda Animalia Homo H. sapiens Hominidae Primates Mammalia Chordata Coniferophyta Anthophyta Coniferopsida Monocotyledonae Coniferales Asparagales Cupressaceae Orchidaceae Juniperus Vanilla J. occidentalis V. planifolia Do not post to Internet

‘Woodpecker’

‘Woodpecker’

Eubacteria Archaebacteria Protista Fungi Plantae Animalia

ANIMALS PLANTS arthropods conifers FUNGI chordates flowering plants annelids roundworms echinoderms ginkgos sac club mollusks fungi fungi cycads horsetails rotifers zygospore- ferns forming flatworms fungi lycophytes cnidarians bryophytes chlorophytes sponges chytrids green algae amoeboid PROTISTANS protozoans (stramenopiles) (alveolates) brown algae red ciliates algae chrysophytes sporozoans oomycotes ? dinoflagellates crown of eukaryotes (rapid divergences) euglenoids slime molds kinetoplastids parabasalids (e.g., Trichomonas) EUBACTERIA diplomonads spirochetes ARCHAEBACTERIA (e.g., Giardia) extreme Gram-positive bacteria chlamydias methanogens halophiles cyanobacteria proteobacteria extreme thermophiles molecular origin of life

Cladistics Cladistics- Classification based solely on evolutionary relationships. Classification of organisms matches their evolutionary history and expresses the history in branching trees known as cladogram. Clade-The entire portion of a phylogeny that is descended form common ancestor.

How do we construct evolutionary trees using cladistics? Identify ancestral and derived traits. Ancestral traits- Traits shared with a common ancestor Most mammals have four limbs, having inherited this from common ancestor. Derived traits- A trait that differs from the ancestral trait in a lineage. Homologous Traits- Traits derived from a common ancestor. Most mammalian limbs terminate in five digits, but in the hooved animals, there is only one. This trait, having only one digit, is a homologous trait and could be used to group all the hooved animals together.

early reptile pterosaur chicken bat porpoise penguin human 1 2 3 4 5 1

Archeaopteryx vs. Pigeon

Difficulties in determining homologous traits Not all resemblances are products of common ancestry. Homoplasy- Some traits are the product of convergent evolution, the evolution of the same trait in different lineages Ex: Australian mammals vs. N. American Mammals

Homoplasy

Species that share a common ancestor should share many homologous traits Therefore, if two species share the same trait, systematists should, until proven otherwise, assume that the trait is homologous, i.e. none of the traits are the product of convergent evolution.

shark mammal crocodile bird fur feathers gizzard lungs heart

Clades

Major Lineages

Constructing a Cladogram Assumptions Evolution of traits is irreversible, i.e. an ancestral trait can change into a derived one, but not the reverse. Each trait can change only once in a lineage.

Constructing a Cladogram Determine an outgroup, a taxon that is closely related to the group whose phylogeny is being constructed, but that branched off from the lineage of the group below its base on the evolutionary tree. You know it’s different from the rest. It’s the one that’s “not like the others”. Select traits that are believed to be homologous. For each taxon, determine whether it has, or is lacking, that trait. (+) indicates the presence of the trait in that taxon. ( - )indicates the lack of the trait in that taxon. Taxa with more homologous traits, have a more recent common ancestor, i.e. they are farther up the tree

CENOZOIC MEZOZOIC ancestral mammal elephants, proboscideans platypus, monotremes kangaroos, marsupials Insectivores, bats shrews, other whales, dolphins horses, other perissodactyls deer, other artiodactyls manatees anteaters armadillos carnivores primates rodents rabbits CENOZOIC MEZOZOIC ancestral mammal