Speciation & Phylogeny

microevolution

effect behavioral, physiology, and morphology of particular species in particular environments

macroevolution

• how new species are formed

• how higher levels of organization come to be

organisms cluster into…

species

taxonomy

• naming and classifying things into an organized, hierarchical system

phylogeny

how things are related (evolutionarily) to one another

• evolutionary relationships among group of species

how do we know how organisms are related?

shared derived characteristics

outward similarity…

is not always a sign of relatedness

convergent evolution

specific evolutionary process: independent development of similar physical traits in unrelated species due to similar environmental pressures

homoplasy

traits that look alike or share a similar purpose but evolved separately

outward difference…

is not always a sign of real difference

divergent evolution

evolutionary process where organisms that come from the same ancestors evolve different traits and splits into different species overtime

when one species splits into two…

• they share some ancestral traits

• differ in some derived traits (relative to a reference group)

synapomorphies

shared derived characteristic that two or more taxonomic groups inherited from a common ancestor

1-7 order

1-7: order

4-7: suborder

5-7: family

5-6: genus

5: species

speciation

evolutionary process by which one ancestral population splits into two or more distinct species

• fundamental evolutionary process

biological species concept

species are groups of organism that naturally or potentially interbreed in nature and are reproductively isolated

reproductive isolation

individuals from one group do not breed successfully with those from another group

anagenesis

gradual change of a population over time, where new ancestral species form without splitting into multiple branches

cladogenesis

a single parent species splits into two or more distinct, independent descendant species

phyletic gradualism

slow, gradual transformation over long periods of time

• often anagenesis

punctuated equilibrium

• statis

• change with speciation

• often cladogenesis

• allopatry: related populations or species live in different geographical regions

ecological species concept

a species should occupy its own unique ecological niche

what does ecological species concepts suggest?

natural selection maintains species boundaries

recognition species concept

species have their own distinct systems for recognizing potential mates

why is reproductive isolation so important?

• prevents gene flow, maintaining differences

habitat isolation

species A & B occupy different habitats like tree limbs and forest floor

temporal isolation

species A & B breed in different seasons, different times of day, or are active at different times of day

behavioral isolation

Species A elicits mates through calls while Species B only responds to dancing

sperm-egg incompatibility

mating occurs but the sperm of Species A is unable to fertilize the eggs of Species B

offspring sterility

hybrid offspring are healthy but reproductively sterile

• like mules

character displacement

competition over resources accentuates morphological differences

• reduces competition for resources

reinforcement

• hybrids will have lower fitness

• selection will favor behavioral and morphological traits that prevent individuals from each species from mating with one another

allopatric

speciation occurring via geographic isolation

sympatric

speciation occurring the same geographic location

• selection favors different adaptations to a similar environment within a single species

• probably quite rare in nature

parapatric

speciation occurring when two populations have continuous distribution and some phenotypes in that distribution are more favorable than others

• new species form through a combination of natural selection and partial genetic isolation

• large, ecologically diverse range

• zone of hybridization: hybrids generally have lower fitness

adaptive radiation

a single kind of plant or animal diversifies to fill many different niches