MACROEVOLUTION & SYSTEMATICS:CHAPTER 5

DEFINITIONS Microevolution: genetic change in a population from one generation to the next

Macroevolution: Processes through which new species arise

WHAT IS A SPECIES? Biological species concept: If

organisms from two populations are capable of breeding naturally and can produce fertile offspring, then they are classified in the same species.

Horse Donkey Mule

X =

SPECIATION The formation of new

species Gene flow keeps

populations similar to one another.

Reproductive Isolation: genetic isolation of populations that may cause them to become incapable of producing fertile offspring.

Gene flow is the glue that holds species together.

SPECIATION: A TWO STEP PROCESS1. Reproductive Isolation

Reduction of gene flow provides opportunity for speciation

Does not always lead to speciation

2. Genetic Divergence Other evolutionary forces

change population enough so that fertile interbreeding is no longer possible

ANAGENESIS: “STRAIGHT-LINE” EVOLUTION

Single species evolving into new species over time

CLADOGENESIS: “BRANCHING” EVOLUTION

Formation of one or more new species from another over time

3 TYPES OF SPECIATION

1. Allopatric speciation-speciation in organisms with no geographic overlap.

2. Parapatric speciation-speciation in organisms with partial geographic overlap.

3. Sympatric speciation-speciation in organisms with complete geographic overlap.

ALLOPATRIC SPECIATION

MODELS OF SPECIATION

PARAPATRIC SPECIATION

SYMPATRIC SPECIATION

Niche: the way of life of a species (How that species fits into the surrounding environment)

Niche partitioning: species evolve to occupy different niches and avoid competition Ex. occupying different

places in the habitat, feeding at different times, being active at different times of the year, etc.

Bees and moths use the same food resource

Bees diurnal, Moths nocturnal

☼ Can’t have two species occupying the same niche in the same area because this will lead to competition.

NICHE PARTITIONING

SPECIATION RATE

Rate of Speciation: depends on # of empty niches

Adaptive Radiation: Rapid diversification by a small # of species to fill many open niches

TEMPO OF EVOLUTION

Gradualism: Macroevolution is a relatively slow and gradual process.

Punctuated Equilibrium: Long intervals of time with little change (stasis) interspersed with short intervals of rapid evolutionary change.

THE BIRTH OF SPECIES

a) Gradualism

b) Gradualism with increase in rate of change

c) Punctuated Equilibrium =Staircase pattern

EXTINCTION The

disappearance of a group of organisms such as a species.

When a species cannot change fast enough to adapt to changes in its environment, it may become extinct.

NEARLY EVERYTHING THAT HAS EVER LIVED IS EXTINCT

PALEOSPECIES

Paleospecies: Identified in the fossil record based on physical similarities to and differences from other species

Assumption: physical similarity = genetic relatedness

CLASSIFICATION

Classification is used to order organisms into categories to show evolutionary relationships.

LINNAEAN SYSTEM OF CLASSIFICATION Hierarchical

classification Involves a number of

categories and subcategories reflecting evolutionary relationships Kingdom Phylum Class Order Family Genus Species

Carl Linnaeus

HOW CAN WE MAKE SENSE OF ALL OF THIS DIVERSITY?

PHYSICAL SIMILARITIES ARE ONLY USED TO CLASSIFY ORGANISMS IF THEY REFLECT EVOLUTIONARY RELATIONSHIPS

Analogous traits: Traits similar due to common function

Homologous traits: Traits similar due to common ancestry

NOT ALL HOMOLOGOUS TRAITS ARE EQUALLY USEFUL FOR

CLASSIFICATION Ancestral trait: Trait appearing early in the evolution of a lineage

Derived trait: Traits that are modified from the ancestral condition

USING DERIVED TRAITS TO BUILD PHYLOGENIES

Analogous Traits Ancestral TraitsDerived (Homologous) Traits

EVOLUTION OF THE COOTIEMOUTH

(PHYLOGENETIC TREE)

QUESTIONS1. What is a phylogeny? 2. What is the difference between

analogous and homologous traits?3. What is the difference between ancestral

and derived traits4. What is the difference between

microevolution and macroevolution?5. What is the biological species concept?7. What are allopatric, parapatric, and

sympatric speciation? 8. What is an adaptive radiation?9. How do you identify a paleospecies and

what are the problems with this method?

HAVE A NICE DAY!