BMS2202 Biodiversity Quiz 1

Phylogeny

evolutionary history of a group of related species

analogous characters arise by…but not…

convergent evolution

common ancestry

name the taxonomic groups

domain

kingdom

phylum

class

order

family

genus

species

Darwin’s ideas of the tree of life

all species come from common ancestor

all species in past and present can trace their ancestry back to single common ancestor

all organisms in tree of life are descended from distant common ancestor

sister taxa

groups that share an immediate common ancestor not shared by any other group

Homology

phenotypic and genetic similarities due to shared ancestry

monophyletic group

ancestral species and all of its descendants

paraphyletic group

ancestral species and some of its descendants

polyphyletic group

most recent common ancestor of members is not part of group

divergent evolution

related species become different due to adaptation to different environments

systematics

scientific study of diversity of organisms and their relationships

sister clade

clades that are each other’s closest relatives

sister species

two species that are each other’s closest relatives

Molecular clock hypothesis

nucleotide substitutions occur at a constant rate

Character-based methods for phylogenetic tree construction

• maximum parsimony: choose tree that requires fewest character changes

• maximum likelihood: chooses tree that makes observed data most probable under specified evolutionary model

• bayesian mcmc: chooses tree in proportion to posterior probability (likelihood after seeing info/models)

Darwin’s 3 hypotheses

1. organisms have variations

2. organisms differ in fitness

3. organisms struggle to survive & only survivors reproduce

Natural selection

• leads to adaptive evolution

• differences in phenotypes of individuals causes some to survive and reproduce more effectively than others

Darwin’s 3 inferences

1. Must be fierce struggle for existence among population, resulting in survival of only small part of each generation

2. Survival is no random but depends partly on hereditary constitution of surviving individuals (natural selection)

3. Over generations, this process of natural selection will lead to continuing gradual change of populations to evolve and produce a new species

4 classical categories of evidence

1. biogeographical: similar species occur nearby in space because they descend from common ancestors

2. paleontological: closely allied species succeed one another in time and live nearby in space because of common ancestor

3. morphological: # shared characteristics=how recently 2 species diverged

4. embryological: embryo is animal in less modified state so it reveals structure of its progenitor

4 types of evolutionary processes

• divergent evolution

  • due to genetic drift & natural selection

  • homologous structures

• convergent evolution

• co-evolution

  • likely when species have close ecological interactions

• artificial selection

Processes that foster microevolution (+ impact on genetic variation)

1. genetic mutation (increases)

2. gene flow (increases)

3. genetic drift (decreases)

4. natural selection (decreases)

5. nonrandom mating (no effect on allele frequencies)

Speciation process

isolation > adaptation > speciation > diversification

adaptive radiation

single ancestral species rapidly diversifies into new forms in response to different environments

2 types of speciation

• allopatric

  • populations separated by geographic barriers

  • no gene flow

  • divergence by adaptation & drift

• sympatric

  • same geographic area

  • reproductive isolation via behavioral, temporal, ecological differences

Derived traits of plants (3 key traits that are absent in charophytes)

1. alternation of generations

2. walled spores produced in sporangia

3. apical meristems

Sporophylls

Sori

Strobili

• sporophyll- modified leaves with sporangia

• sori- clusters of sporangia on undersides of sporophylls

• strobili- cone-like structures formed from groups of sporophylls (helps spore dispersal)

What plants are homosporous and which are heterosporous?

Homosporous: most seedless vascular plants

Heterosporous: some seedless vascular plants, all seed plants

Similarities between plants and algae

• multicellular, eukaryotic, photosynthetic autotrophs

• some algae have cellulose in cell walls & chloroplasts containing chlorophyll a and b

What adaptations allowed chatophytes to move to land?

• natural selection favored algae that could survive periods of dryness

• sporopollenin- polymer that prevents zygotes from drying out

Advantages & disadvantages to life on land for plants

advantages:

• unlimited sunlight

• abundant CO2

disadvantages:

• maintain moisture in cells

• support body against gravity

• reproduce & disperse offspring without water

• obtain resources from soil and air