Bio 180 exam 3

morphological species concept

species are groups that possess unique anatomical features
^only method that works w/ virtually all fossil species
^cons:
*many species can't be distinguished by unique anatomical traits (diff species but have very similar traits (cryptic species))
*subjective, there is morphological var w/in species too (is it a separate species or just within-species variation?)
*tricked by convergent evolution
*diff life stage of organism can be mistaken for diff species (ex: caterpillar to butterfly)
*sexual dimorphism (same species, but diff sexes have very diff traits)
_{^{*morpho - shape/form}}

biological species concept

species are identified by reproductive isolation (no gene flow occurring btwn them, can't/don't interbreed -> speciation)
^pros: easy to do
_{^{*evidence: reproductive timing (mating), physical barriers btwn pops}}
^cons:
*only relevant to eukaryotes that undergo sexual reproduction, can’t apply to species that don't sexually reproduce
*can't be used for fossil species
*if 2 pops aren't in physical contact/no opportunity to mate, difficult/impossible to know whether they are considered diff species

phylogenetic species concept

pop represents an independent twig on the tree of life (smallest monophyletic groups on a phylogenetic tree, the tips of the tree)
^more objective bc uses DNA sequence data _{^{to identify indep twigs on the tree of life}}
^con: can lead to over-splitting _{^{(some species have DNA sequences that change rapidly, each indiv in the pop has a unique DNA 'fingerprint,' is a unique sequence in a small group of indiv separate species or not?)}}, hard to use for fossil record (limited by where u can get DNA from), some groups don’t have a (good) phylogenetic tree

speciation

process that creates new species/types of organisms; splitting event where 1 species breaks into 2 or more separate species
^creates biodiversity

steps of speciation

1. genetic isolation (2 pops represent indep entities bc separated)

-interrupted gene flow btwn 2 pops of the same species, allele freqs no longer homogenized

2. genetic divergence (become more and more unlike genetically, becoming distinct species)
-split from ancestral group, indep daughter pops
-isolated pops free to diverge, mutation/natural selection/genetic drift _{^{(the other 3 evolutionary processes)}} act on descendant pops independently
-diverge from: diff environments, natural selection favoring diff alleles, drift (fixation/loss of diff alleles), mutation

monophyletic group

consists of an ancestor and all of its descendants _{^{('one-kind' group)}}
*aka lineage, clade
^several monophyletic groups can be nested w/in one another!
^taxa labeled at the tips are always a monophyletic group
^synapomorphies define monophyletic groups

homology vs. derived similarity vs. synapomorphy

homology - shared trait/genes bc inherited from the same common ancestor

derived similarity - NEW character state appears in ancestor, then inherited by its descendants

synapomorphy - any characteristic/trait that is shared by other members of the monophyletic group but isn't found in other groups; a trait 1 group has that no one else does
*unique characteristics
_{^{^arise bc once an ancestor has split into descendant groups, unique traits will evolve in each descendant group and be passed along to their descendants w/ more splitting events (type of homology) (identify discrete monophyletic lineages on the phylogenetic tree)}}

homoplasy vs. homology

similarity in traits that is due to independent evolution and NOT inherited from the same common ancestor _{^{(same-form) (ex: bats/birds have wings)}}
^aka convergent evolution
_{^{*can’t predict abt genetic/developmental similarity}}

vs.

similarity in traits due to common ancestry _{^{(same-source)}}

parsimony

simplest explanation for an observation/phenomenon is most likely correct

character and character states

heritable features/traits that can be compared across organisms; variations in features/diff forms of a character
^ex: character is body covering, character states are scales, feathers, hair  

ancestral similarity

degree of genetic/physical/molecular likeness btwn organisms/pops/DNA sequences that is inherited from a common ancestor (indicative of common ancestry, but not indication of a monophyletic relationship in which all the organisms in the group are more closely related to each other than to any other organism)
^ex: lizards/crocs both scaly bodies bc share a common ancestor that had scales, but crocs share a more recent common ancestor w birds than w lizards even tho lizards/crocs both scaly

more closely related if?

share a more recent common ancestor (closer to present/tips of the tree) (so more genetically similar)

Types of similarities

• derived -> monophyletic

  • ^one snip test (cut once, get all the groups you want and ONLY the ones you want)

  • ^homology

  • ^defined by synapomorphic trait

  • ^share a more recent common ancestor

• ancestral -> paraphyletic

  • ^same/similar trait but NOT more closely related to one another than any other organisms

  • ^an ancestor and some, but not all, of its descendants

  • ^related, but not 1 snip (mult cuts)

• convergent/parallel -> polyphyletic

  • ^homoplasy

  • ^due to natural selection

  • multiple/indep origin of the same character state (often bc diff species adapt to similar environments/pressures)

types of speciation

• allopatric (‘diff land’) - pops separated geographically, so evolutionary forces act on them independently  

  • dispersal (founder event) 

  • vicariance – split of an existing range into fragments

• sympatric (‘same land’) - gene flow stopped even tho still in same area  

  • ex: diff pollinators (genetically isolated), divergence from selection for traits that attracted diff pollinators

succession of types

observation that extinct species found in rocks of a particular geographic area are similar to species that are living today in the same area

adaptive radiations

rapid speciation/diversification of a single lineage into a large number of species
^each adaptation allows them to exploit diff resources/habitats
^identify: a single lineage (trace back to 1 species/ancestor), rapid speciation (fast!), and species exploit a wide array of resources/habitats (food, environment)

niche

the range of resources/environments that a species uses (how/where it makes a living)

morphological innovation

a novel trait that allows indivs to exploit resources in a new way (ex: bipedal, can use hands to grasp/manipulate objects)
^new niches
*adaptive breakthrough

relative dating/geologic record

when researchers use observations abt rock formations to conclude if rocks are older/younger than each other
^rock formations horizontal when first created
^younger rock layers on top
^if crack filled by lava/rock-forming sediments, the 'intruding' rocks = younger than the layers around them

absolute dating/radiometric dating

when scientists use data from radioactive isotopes trapped inside rocks to assign a chronological age to those rocks
^use decay rate of the radioactive isotope and the relative amts of that isotope/the element produced when it decays
^years/half life x # of half lives = # of years passed (how old)
^best to use isotopes w/ longer half-lives for older rocks and shorter half-lives for younger rocks

!!! flip

_{^{bilateral symmetry enhances directed movement, improves sensory perception, and facilitates efficient foraging and feeding
^associated w/ cephalization (concentration of sensory and nervous structures at the anterior end (head)) -> more efficient/directed mvmt and navigation thru environment, coordination (*humans have!)}}

ppl experiencing symptoms of infection should take appropriate antibiotics to reduce pop of bacteria to decr symptoms

what events commonly precede adaptive radiations and why?

• mass extinctions (competitors wiped out)

• indivs colonize new areas

• evolution of key traits (morphological innovations)

bc new ecological opportunities/innovations
^all 3 have availability of (new) resources (empty niches, specialize in specific thing) + low levels of competition w/ other taxa
+selective pressure, new ecological niches can be filled (indivs can exploit new types of resources)

How to tell if a trait is from homology or homoplasy/convergent evolution?

look for recent, shared common ancestor on tree w/ the trait 

.
ancestor and all descendants have trait = homology, synapomorphy  

.
trait arises separately = homoplasy, convergent evolution

Adaptations that allowed plants to colonize land and diversify

• land plant synapomorphies

  • cuticle (waxy covering of plant tissue) to avoid drying out (prevent water loss)

  • stomata (openings in epidermis) for gas exchange (in CO2 & H2O, out O2) in photosynthesis

• vascular tissue (group of cells that transport fluids (water) and give structure)  

  • synapomorphy of vascular plants  

  • _{^{not free floating, need structure to deal w/ gravity}}  

  • helps w/ photosynthesis; works w/ stomata  

• seed plant (angiosperms and gymnosperms) synapomorphies

  • pollen (plant sperm) (cells encased in a tough coat)  

    • can be transported thru wind, animals, water  

    • for outcrossing (transport gametes w/o drying out)  

  • seed (embryo w/ a food supply (for nutrition) surrounded by a tough coat)  

    • transported away from parent by wind, animals, water  

    • far dispersal, parents/offspring not competing for sunlight/water/nutrients  

• angiosperm synapomorphies

  • flower (attracts pollinators)  

    • greater rate of outcrossing, more genetic diversity  

  • fruit (aids seed dispersal) 

ecology

the study of how organisms interact with each other/their environment 

behavior

the study of what organisms do, how they do it (in terms of genetic/neuronal/hormonal mechanisms), and why (in terms of fitness) 

behavioral ecology

the study of how organisms make decisions when they interact w/ various aspects of their environment
_{^{^eat, live, communicate, mate w/?}} 

sexual selection

a type of natural selection that favors indivs w/ traits that increase their ability to obtain/choose mates
^can operate against survival interest (Fisher's runaway selection)
*diversity of sex (mating/reproductive strats differ w/in and across species/pops/indivs)