Unit 3 Study Guide Evolution

Define microevolution. Name an example.

Biological evolution that occurs within individual species or populations

Flower color

Define macroevolution. Name an example.

Biological evolution above the level of an individual species

Flowers from many plants

Define strong interference. What does this have to do with causation and confidence?

Testing hypothesis or set of alternative hypothesis using carefully constructed experiment that control critical factors

Causation can often be inferred with high degree of confidence

Microevolution is usually tested by this since we can subject different organisms to niche environments

Define weak interference. Can we control it?

Testing a hypothesis when experiments are not fully controlled because of material or fiscal constraints or when well-controlled experiments are impossible

Macroevolution is usually tested by this since we cannot measure long time scales and spatial scales

What are 3 ways we can minimize problems with weak interference?

Take account of other information or well-supported theories when developing hypotheses

Germination and oil experiment**

Develop hypotheses that are as specific as possible (minimizes the number of factors that may affect what is being studied)

Use multiple lines of evidence to support hypothesis

What was the thought process on Pre-Darwinian speciation? What are the 2 concepts associated with it and define them?

The creation of the taxonomic system, it was an intuitive sense of species

2 concepts associated:

Phenetic Species Concepts: species determined by appearance

Typological Species Approach: species defined by reference to the specimen (type) that fits species best

Explain Post-Darwinian Phenetics. How were species defined?

Post Darwinian: measure as many traits as possible on organisms

Species were defined by cluster stats to distinguish them

"Patterns without a process"

Define vertical vs horizontal concepts.

Vertical: concepts that define species from the time of inception until they speciate or go extinct

Horizontal: concepts that define a species at a moment in time

Explain the biological species concept. Is it horizontal or vertical?

Biological Species Concept #1: HORIZONTAL CONCEPT! An interbreeding group of organisms that is reproductively isolated from other organisms [Ernst Mayr and Dobzhansky]

Rooted in populations genetics perspective

No asexual species involved

Interbreeding group binds members of species together

Name the 6 types of prezygotic isolation mechanisms and define each.

Geographical isolation: separated physically and spatially

Ecological isolation: same area, different parts of area

Temporal isolation: different seasons or times, like day or night

Behavioral isolation: having different behavioral techniques, bird calls only attracting certain mates

Mechanical isolation: the parts don't fit correctly to possibly mate

Gametic isolation: zygote never forms, usually chemical issue from egg

Name the 3 types of postzygotic isolation mechanisms and define each.

F1 hybrid inviability: hybrids die due to incompatible development programs

F1 hybrid sterility: they have offspring but it cannot have offspring, mules

Hybrid breakdown: genetic failure in F2, all F2 seeds die

Explain the one hybrid breakdown mechanism.

2 species interbreed → F1 offspring occur [epistatic success] → random assortment in F2 sometimes will work and create new offspring, but sometimes won't

Define the recognition species concept. Name an example.

Recognition species concept: a group of organisms that have a "shared mate recognition system" SMRS which they use to identify appropriate males

Bowerbirds: females dont care for males that don't match their gene pool's call

Works well with animals that have specialized mating rituals for choosing mates

A role for sexual selection in speciation

Behavioral isolation! ← example of this

What does the shared mate recognition system not work well for? Name an example.

Does not work well for organisms that

Release gametes into air or water

use vectors like bees, to spread gametes on flowers

Explain the difference in the biological and recognition species concept and their similarity.

They differ by

The mechanism in which their gene pool is maintained

They are similar because they are both reproductive species concepts

What 2 situations is BSC right?

Species with low mating costs for males "mate and move on" - isolating mechanism

Species that lack perceptual systems for recognizing mates - plants

What situation is RSC right?

Species with high mating costs for males "both sexes deeply invested" - SMRS

Explain the cladistic species concept.

Lineage of interbreeding organisms that begins when its parental lineage is divided into two species and ends when it extinct or speciates

What is anagenesis?

Gradual evolution of a species that continues to interbreed without speciating

Speciation without splitting

What are crypto species? Name the examples and the problem.

CryptoSpecies: Individuals look alike, however genetics are different, and this is only true because there is no gene flow between the two.

If they were interbreeding, their unique alleles "private alleles" would become shared, therefore they are not mating at all.

Oak Titmouse vs Juniper Titmouse

Name the 3 modes of speciation and define them.

Allopatric: one population → separated to two areas → populations differentiate → [may or may not occur] differentiated populations become sympatric, MOST common case.

Parapatric: one species with a contact zone that may hybridize, LEAST common case.

Sympatric: single population → no spatial speciation → some individuals stop breeding with one another

Explain small vs large scale events for allopatric speciation.

Large scale: oceans, mountains, plate tectonics [vicariance events]

Small scale: peripheral isolates

What 3 forces would be expected to genetically differentiate a population, and what's their likeness?

They adapt to their environment

Selection: different sides of the mountain

Drift: not likely, but possible

What's the minimum number of loci needed for genetic incompatibility?

2

Explain Dobzhansky-Muller incompatibilities. Name an example and explain what occurs. What's another name for this?

Each population gets a new allele fixed but at different loci, and the hybrid as a completely new allele combination due to both loci that makes it an incompatible, usually fatal hybrid

Platy Fish and swordfish: if you cross F1 X swordfish, it will get melanoma and die

Occur because the swordfish does not have loci that protect it against the tumor causing locus that it combines with, so 25% chance of death

Hybrid breakdown

What 2 ways do deleterious mutations go to fixation?

Hitchhiking

Genetic drift, if selection is weak

What are peripheral isolates? How does this affect the population?

Small groups if individuals that break off from large group and form new species

Population reaches places it would not normally

Occurs because the population expands while conditions are favorable and contracts when they are not

Name another way to get a peripheral isolate.

Founders Effect: immigration of small number of individuals to a new habitat

What is the proof for allopatry, explain the experiment and control.

Dodd Experiment Steps

Gather sample of wild flies

Randomly assign food substrate

4 allopatric populations on each, 2 mediums

Allow to evolve for several generations

Test for mating preference

Control: a starch population mates with another starch population, same for maltose [these are the 2 mediums]

What is the isolation index?

II = # of individuals from their own population - number that choose other population / total

What were the 3 key points of the Dodd experiment?

Mating preference accompanied by diet

Pre zygotic isolation produced quickly

Not clear whether drift could play a role or not, just wasn't tested for

Same pattern seen in other species

Why would selection on a trait create a mating preference? 2 ways.

Hitchhiking: if selection is doing well will favor the trait of mating preference

Pleiotropy: gene that makes one do well on medium also affects mate choice

Explain the ghost of selection past.

Past preference due to prior selection of certain traits and makes it more likely it is isolated

Seen in developmental biases

What are developmental biases?

Produced by prior evolutionary history

Music taste in humans

Females develop mating preference based on odors of food environment when they are maggots

Bias created by selection for finding a more compatible mate "pre-adapted"

Explain the natural experiment of species relatedness and vicariance. Name the example.

After a vicariance event, each branch on a tree will separate into two

Panama Isthmus example

Explain clinal variation and the two examples.

Based on where organisms are, it's a cline of size or particular trait

Size of male house sparrows in North America

Up north they are larger to survive the cold

In the south they have no need to be large, so are smaller due to warmer weather

They are effectively isolated from one another

Streptanthus glandulosus

Further apart = lower gene flow = lower post-zygotic fertility

Explain primary vs secondary contact.

Primary contact: the populations have never been in contact and can interbreed

Secondary contact: when an allopatric population comes back together

What are the 3 outcomes that may occur if allopatry is lost.

Speciation is complete

The incipient species freely interbreed and become common gene pool

Incipient species undergo reinforcement.

Explain reinforcement.

If the incipient species have been selected for different environments, they hybridize and are less likely to be more or as fit than parents.

Explain assortative mating.

Mating with individuals similar to one's self

Gene flow (migration) due to hybridization tends to merge parental types if.. (2 things)

Assortative mating doesn't evolve quickly

Hybrids are mildly unfit relative to parents

Explain the problem with reinforcement.

If several loci are involved, recombination will often unlink traits that differentiate incipient species, creating less favorable alleles

Relationship between what they prefer and where they live best will decouple within 2 generations

Explain incipient species.

A group of species that is about to become a separate species, but not quite yet done speciating

Explain parapatric speciation. Name an example.

Retains contact zone to hybridize, creating a stepped cline

Serpentine soil creates cline, as only a few can survive at the top, radical environmental change

The beach for humans and fish

Tension zone may be created which is when hybrids are less fit than parents and reinforcement may be favored to evolve and speciate

Explain sympatric speciation. Define both general classes of it.

Same general area and they stop inbreeding

Two classes:

Gradual sympatric speciation: prior to speciation, species is limited in habitat

Instantaneous speciation: they undergo hybrid speciation

Explain host shifts. Name an example.

Movement of parasites, disease or insects from one host to another, causing behavioral isolation

Tephritid fly goes from hawthorn fruits to apples and they genetically differentiated based on the fruit they inhabit

Developmental biases at play here

Name the two types of hybrids for instantaneous speciation and explain how it works, as well as how they pertain to backcrosses for one of them.

Allopolyploid hybrids: complete diploid gametes are inherited from two different species (4n)

If this makes a backcross to its parent, it will create a triploid offspring, which will be sterile

Strong post-zygotic isolation

Diploid hybrids: haploid gametes from 2 species combine to produce diploid hybrid (2n)

Explain and define an example of diploid hybridization.

Speciation is not instantaneous and may backcross relatively easy to either one of its parents

2 sunflower species

Explain the 2 conditions to provide diploid hybrid speciation and examples.

Selection for survival in different habitat than either parent species [lowers gene flow and allows time to differentiate]

Anomalus lives in sand dunes and neither parent does

Chromosomal rearrangements: promosts postzygotic incompatibility

Sunflowers, but almost always produces sterility

Explain how phylogeny is a murder mystery.

We know a murder happened (speciation)

Body is found (Present day species)

Clues were left behind (evidence and data)

We make knowledge, science and logic to figure it out (inferences)

We figure out the murderer (phylogeny)

What are the 2 criteria to classify things? Explain.

Objectivity criterion: reasons for groups must come from external, real,and unambiguous properties of nature

Naturalness: characters used to determine common features of group produce the same classification as characters used to determine the group phylogeny for another

What is character conflict?

Characters indicate different groupings

What is a sister species?

Species derived from the MRCA

Define homology.

Character shared between species because of common descent; inherited from common ancestor of species

Define analogy.

Characters shared due to convergence

Similarity due to either chance or common selective pressures

Define similarity.

Two characters appear alike with each other without making any claim about common descent or convergence

Define symplesiomorphy.

Inherited from a MRCA of a group but not all descendants of the group have the character

Define apomorphy.

Derived homology vs plesiomorphy being ancestral homology

Define autapomorphy.

Derived in single lineage

Define synapomorphy.

Derived in many lineages

Define monophyletic groups and how they are created and what they are used for.

All descendants come from single common ancestor

Created using synapomorphies

Only used for cladistic classification

Define paraphyletic group and how they are created

Some but not all descendants of MRCA

Used in Linnaean classification

Define polyphyletic groups and how they are produced.

Species grouped but not due to the same common ancestor

Produced using analogies

Explain the phylogenetic approach.

Uses characters of organisms, hierarchy exists independently from methods used to discover it

Uses synapomorphies to determine relationships

Explain the cladistic concept.

Groups are related due to one another by their MRCA

Differ a cladogram vs phylogram vs chronogram.

Cladogram: only topology

Phylogram: topology and evolutionary distance

Chronogram: phylogram with branch depths indicating divergence times

What is the evidence for the phylogenetic method?

Similarity of species in their shared derived characters (synapomorphies)

Practically: species are grouped with other species that have the most shared derived characters

What is parsimony and its justification?

Parsimony is simplicity, least evolutionary change

Works if evolutionary change is infrequent relative to rate of speciation

What are the steps to produce a tree?

Find simplest and shortest possible unrooted tree

Root the tree with the branches and species

What are the 3 principles to determine homologies?

Homologous characters show same fundamental structure

Revealed by deeper look at nature of structure

Homologies have same fundamental relationships to surrounding characters

Bones bearing relation to other bones

Same embryonic development in different groups

Similar adult characters that develop by different processes are not as likely to be homologous

What are the 3 criteria for determining ancestral and derived homologies and their shortcomings?

Outgroup comparison: use sister group of ingroup to determine ancestral character state

Use parsimony to judge most likely set of events

SHORTCOMING: different outgroups can sometimes give conflicting information about which character states are ancestral

Embryological criterion: general features of large group of animals appear earlier in the embryo than special features

In other words, special features evolved later than general features

SHORTCOMING: some derived features get inserted into an older developmental sequence

Think about metamorphosis

Paleontological criterion: fossil record

Features in older fossils are ancestral to ones found in younger fossils

SHORTCOMING: incompleteness of the fossil record can give misleading view of what is ancestral and derived