Evolution

Question 1

evolution 1

Answer 1

• All life forms are derived from previous life forms
• Genetic variation underlies evolutionary change
• Evolution yields anatomical and functional alterations over time
• changes in anatomy and function!
• Adaptation is specialization in response to particular environment
• Speciation is formation of distinct, reproductively isolated, life forms

Question 2

Speciation

Answer 2

Speciation is formation of distinct, reproductively isolated, life forms

Reproductively isolated is how species are defined, life forms

Question 3

Genetic variation

Answer 3

Random mutation produces genetic variation

Polymorphisms = sequence changes of different alleles

Gene pool = collection of all alleles for all genes in a population, ALL GENES IN POPULATION

Population = all individuals of a species in the same place at the same time, in same place at the same time*** not technically part of the same population of people who lived in NY 200 years ago**

Question 4

Polymorphism

Answer 4

= sequence changes of different alleles, may have nothing to do with genes for different traits; even in parts of DNA can identify polymorphism in population some ppl have letters AAA in that spot, some have AAAT just part of variation you find in a population

Question 5

Gene pool

Answer 5

Gene pool = collection of all alleles for all genes in a population, ALL GENES IN POPULATION

Question 6

Definition of population

Answer 6

Population = all individuals of a species in the same place at the same time, in same place at the same time*** not technically part of the same population of people who lived in NY 200 years ago**

Question 7

Genetic equilibrium

Answer 7

• means no evolution going on no change in allele frequency
• pretty rare and maybe impossible to be in genetic equilbirum forever, but true enough for periods of time that the model is worth using sometimes*
• so in order for a population to be in genetic equilbirum:

1. Mating is random
2. NO MUTATIONS, no net mutation
3. Large population size
4. NO migration in or out of population
5. NO natural selection

Question 8

Genetic equilibrium 2

Answer 8

Genetic equilibrium = no evolution = no change in allele frequency

Five conditions must be met for genetic equilibrium

Mating is random

Net rate of mutations is zero (i.e., A ← → a equal)

Large population size

No migration in or out of population

No natural selection

payoff for making these assumptions can use hardy weinberg assumptions/equations

Question 9

Hardy-Weinberg equilbirum

Answer 9

key here p and q represent frequencies of alleles,

p dominant allele; q recessive allele will be decimals of less than 1

like .2 and .8= 1 which is 100% of alleles for that genetic locus in the population, we are assuming here in this version of Hardy Weinberg assuming only too alleles for this gene** we know out there there are some genes where there are more then 2 allleles, but Hardy-Weinberg assumes 2 for dominant and recessive

Question 10

Hardy-W equ. 2

Answer 10

Hardy-Weinberg (HW) principle governs allele frequencies during genetic equilibrium

HW as applied to a two allele system (Bb):

p = allele frequency of dominant allele (B)

q = allele frequency of recessive allele (b)

p+ q= 1

Example: 75 BB, 125 Bb, 50 bb animals in population; p = 275/500, q = 225/500

Punnett square with allele frequencies dictates that square of equation is also true:

p2 + 2pq + q2 = 1 p2 = freq BB 2pq = freq Bb q2 = freq bb

Therefore, allele frequency is constant in each generation

Can calculate all frequencies from frequency of recessive phenotype (q2)

Question 11

Hardy-Weinberg eq 3.

Answer 11

p² + 2pq + q² = 1

p² = freq BB 2pq = freq Bb q² = freq bb

Therefore, allele frequency is constant in each generation

Can calculate all frequencies from frequency of recessive phenotype (q²)

THE frequency of those genotypes and individuals in population, so first equation p+q=1 tells you abotu frequency of the alleles, this other equation tells you about hte frequency of different kinds of people or animals of genotypes you find in the population

for ex. this equation tells us if maybe individual homozgyous domiant, homo recessive, hetero of allele etc.. if you want to know frequency of homozygote individual is p2, homozgous recessive is the q2

if studying population homozgous recessive disease, if out of 100 ppl in population 1 person has the disease, telling you .01 is q² which is by the easiest thign to measure in population; usually way in the easiest thing to tell, if see how many individuals in population have recessive phenotype and make it a decimal that is giving you q², can also look at a populaton and see what portion of people have the domiannt genotype but not as helpful information do not know if homozgoute or heterozgyote, can be part of p² group or 2pq cannot tell unless squence genomes, but if showing up with homogzgote recessive knwo genotype if know q² can find q then find 2+p =1 then find p….

Question 12

Frequency in HWE

Answer 12

if they say 20 individuals out of 100 have homoz. recessive genotype or homozgous recessive then 20 out of 100 would be genotype too, then the frequency would be 20/100 but make it a decimal so .2

same if population has 200 ppl, 40/200 would also be hte same as 20/100 also .2 in this case for the frequency in this case*

so may have to set up that fraction in order to get the frequency and then onc eyou have the frequency that decimal can use hardyweinberg equation

Question 13

Evolution if violate any of the 5 things….

Answer 13

if violate any of 5 things mentioned population is evolvign! so if net rate of mutaiton is greater than zero, or population size is really small get what is calld genetic drift or migration in or out also called gene flow can change new people coming in means no combination of alleles coming in

Genetic equilibrium ≠ evolution

During evolution, allele frequencies are changing

If any one of five conditions is occurring in a population, evolution is occurring:

Net rate of mutation > 0

Natural selection

Mating is nonrandom (sexual selection)

Small population size (facilitates genetic drift)

Migration in and out of population (gene flow)

Question 14

natural selection

Answer 14

Natural selection is the major driving force for evolution

Acts on PRE-EXISTING genetic variation in population

Selection increases frequency of helpful traits, decreases negative traits

Selects for individuals, not the group as a whole

Group selection (idea that evolution can sometimes select for group) is controversial

Question 15

natural selection 2

Answer 15

watch out on mcat- say being treated with a certain antibiotic, the antiobiotic kills 99% of the bacteria causing your infection but 1% of that bacteria by random lucky chance has some mutaiton allows you to resist antibiotic being treated with so the presence of that antibiotic is then creating a selection pressure favoring bacteria that have resistance gene and can thrive even in the presence of that antibiotic so then the resistance bacteria will proliferate and become the dominant form of bacteria in your system overtime** MCAT will definitely test that concept but the way you would describe what is happening selection pressure in favor of resistant bacteria cells, or can say cells able to grow in the presence of antibitoic were favored, thrived able to pass down genes

what would be the wrong answer choice would be to say when antibiotic was intrdocued that CAUSSED some genes to mutate that caused mutations NOO just favors mutaitons that some lucky little cells happen to have because of sponatenous mutaiton*** doesn’t cause it it favors***

Question 16

Fitness

Answer 16

The more an organism or individual passes on its genes the more fit it is! so the way this has been tested on the MCAT which of the following individuals i teh most fit, 18 year old track star or 85 grandma with arthritiss, in this context the grandmother is more fit than the kid because she has passed on her gene more***

test difference btw evolutionary fitness and atheltic fitness under other circumstances*

Question 17

Fitness 2

Answer 17

Reproduction generally yields more offspring than can be supported by environment

Fitness reflects ability of an individual to survive and reproduce

Two components of fitness: mortality and fecundity

Mortality = death

Fecundity = # of offspring

Fitness is specific to a particular environment

Drought resistant plants are more fit in desert, but not in rainforest

If organism has higher fitness than peers, frequency of its alleles will increase

Question 18

Fecundity

Answer 18

Fecundity = # of offspring

Question 19

Inclusive fitness

Answer 19

A gene maximizes its chance of survival by promoting the survival and reproduction of similar and closely- related individuals

Related to the concept of kin selection

Used to reconcile cooperation between organisms with the idea that genes “selfishly” promote their own survival

Example: animals sacrificing themselves so that a group of relatives survive. Ultimately, this will cause more copies of their genes to exist

Question 20

Inclusive fitness 2

Answer 20

From darwin’s point of view, want to pass on our genes! But it is allso true when our siblings or cousins have kids we want this, the idea of inclusive fitness takes that into account sometimes we will make sacrifices for other members of our family from darwin point of view can explain that by saying when our relatives reproduce genes that we share with them are getting passed down so can make sense of it even from within this very genetically focused perspective

Question 21

Nonrandom mating

Answer 21

In environment, mating is generally nonrandom = sexual selection

Some phenotypes are preferred mates

Individuals may prefer phenotype similar to their own → positive assortative mating

Individuals may prefer phenotype dissimilar to their own → negative assortative mating (opposites attract)

Preferred mates have higher fecundity (average # offspring) more genetically productive kind of mating*

Question 22

genetic drifit

Answer 22

change in allele frequencies that are not just random, when populations are small tend to be changes in allele frequency because of genetic drift

2 examples: bottleneck effect and founder effect

Question 23

bottleneck

Answer 23

natural disaster dramatically dec size of population

alleles that reamin after diseaser are over represented by chance, another allele can be removed from population becuase rare to begin with and everyone who had it died, so can change allele frequency by cutting down population randomly*

Question 24

Founder effect

Answer 24

similar idea, takes smaller population group; story of migration group some small part of the population moved to a new place and founded a new population maybe came to the new world from europe or subgroup of population went somehwere else, in new population they found different than they were in original population that the colonists came from

key is it is a different population, bottleneck effect everyone stays in oen place lots of ppl die; founders effect think about europeans coming to new world, point is both of those scenarios create changes in allele frequency** and that is evolution, evolutionary change

Question 25

Genetic drift, bottleneck effect, founder’s effect

Answer 25

In small populations, allele frequencies more likely to change stochastically (randomly)

Example: allele frequency is 10% in two populations (1000 organisms vs 10)

So, 100 alleles in first population, but just 1 allele in second

By chance, allele much more likely to be eliminated from second population

As a result, small populations undergo genetic drift

Bottleneck is an example of genetic drift

Bottleneck is a rapid decrease in population size, eliminates most alleles

Bottleneck reflects adverse selective pressure (famine, disease, etc)

Remaining survivors carry just a few alleles

When population re-expands, low genetic diversity is dominated by “founder” alleles

Question 26

Classic example two ponds separate but close to eachother….

Answer 26

heavy rain ponds become two ponds, that would be suddenly all alleles are able to mix together

GENE FLOW

Question 27

Gene flow

Answer 27

Separate populations have different gene pools

Mixing of populations transfers alleles

Genetic diversity increases within population, decreases between populations

Example: flooding links two previously separate frog ponds

Question 28

Bottleneck effect vs. founders effect 2

Answer 28

Bottleneck is an example of genetic drift

Bottleneck is a rapid decrease in population size, eliminates most alleles

Bottleneck reflects adverse selective pressure (famine, disease, etc)

Remaining survivors carry just a few alleles

When population re-expands, low genetic diversity is dominated by “founder” alleles

Question 29

species and speciation

Answer 29

Species is a population that can interbreed with itself but not other species

All members can interbreed and produce viable fertile offspring

One species placed in different environments → evolution and speciation

Two groups different species if environmentally isolated, cannot mate with eachother and produce fertile offspring; or can be in same place but not be able to reproduce with eachother***

speciation defined as: the formation of new and distinct species in the course of evolution.

Question 30

REPRODUCTIVE ISOLATION OF SPECIES

Answer 30

categorized into prezygotic before fertilization maybe reproduce in differnt places, different courtship rituals, or gametes do not stick together properly

maybe they do reproduce but progeny are steril or progeny die, so for whatever reason in process reproduction doesnt work properly ex mule sterile

Question 31

Reproduction isolation of species 2

Answer 31

Several barriers to interbreeding of species

Barrier can be prezygotic = before fertilization

Reproduction in different times and places (e.g., seasons)

Different courtship rituals

Mechanical incompatibilities in copulation

Gametes may be incompatible (e.g., sperm cannot bind and get into egg)

Barrier can be postzygotic = after fertilization

Progeny may be sterile (e.g., female horse × male donkey = sterile mule)

Progeny may not complete development

Progeny in second or later generations may be inviable

Gene leakage = gene flow between species

Question 32

prezygotic

and

postzygotic

Answer 32

Barrier can be prezygotic = before fertilization

Barrier can be postzygotic = after fertilization

Question 33

Ecological Niche and Competition

Answer 33

Where an organism or population lives and reproduces

Defined by conditions necessary for growth and survival (food, temperature, light, etc)

Ecological niche includes competitive interactions among populations

Populations indirectly compete for limiting resources or directly interact (e.g., predation)

No two populations can occupy the same niche!

One population will move out, die off, or evolve to occupy another niche

Symbiotic relationships between species (mutualism, commensalism, parasitism)- living very closely with eachother, three kinds

mutualism= ++

commensalism= +/0 one benefits other one doesn’t care

parasitism= +/- situation one species benefits other is harmed by interaction

Just b/c cannot have two populations being in the same place in the same way

Question 34

Optimal foraging theory

Answer 34

Idea from ecology that animals forage in such a way as to maximize their energy uptake per unit time- basically organsims are smart about foraging if can stay where they are eat little berries, low cal but plentiful and do not have to go anywhere will do that and not expend a lot of energy, if can get enough calories where they are they would only make a difficult journey if they needed to so if the bear runs a few 100 miles get better food or more nutrient rich food, but this theory says that organisms is aware of tradeoff will not run 200 miles for nothing if organism expending a lot of energy to get food has to be high calorie and worth it

Organisms adapt strategies that encourage them to intake the most calories while exerting the least effort

Different foraging strategies have evolved depending on both an organism’s environment and how much that environment has changed

An unstable environment will lead to a more flexible diet

Question 35

Evolutionary game theory

Answer 35

The application of game theory to understanding the strategies that organisms in a population use in competition

Unlike in classical game theory, the goal is not the “best” strategy, but a strategy that is stable against others in a population

Often used to explain phenomena between species such as co-evolution and cooperation

Basically game theory scenarios ppl cooperate with eachother, choices individuals make in differnt scenarios if everyone cooperates everyone gets biggest reward if evyerone chooses to cooperate and you don’t then you are screwed so it show you decide to relate to other players, cooperation vs competition in context of game theory some ppl tryign to apply this to evolution and talk about choice btw competion and cooperation

Question 36

types of selection

Answer 36

Most phenotypic traits are polygenic = controlled by many genes

Most traits have a bell-curve distribution around a mean (e.g., height)

Three different kinds of selection

• Stabilizing selection
• Directional selection
• Destabilizing selection

Question 37

stabilizing selection

Answer 37

eliminates extreme phenotypes, narrows curve around mean

if environment really stable, whatever color most common see more and more mice with phenotype that is facored like in this case medium fur*

Question 38

directional selection

Answer 38

• favors one extreme over the other, shifts mean value
• now what happens is htere has been some kind of enviornmental change, maybe there are examples from industrial revolution buildings dirty animals darker coloration could hide better so did better, something changing what phentoype is most favored in this environemnt
• so maybe going further dark phenotype more favored, most favored phenotype is shifting one direction or another!

Question 39

destablizing selection

Answer 39

• eliminates intermediate phenotype, splits distribution in two
• Destabilizing selection may promote speciation
• environemnt becomes pathcy, if light fur can go to one place, dark fur can go ot another place, but if medium fur stuck
• so here get two distinct phenotypes within population favored, destablizing selection can in some cases lead to sepciation
• if light colored mice hang out in one environment adn dark colored mice hang out in another area and stop interacting with eachohter can no longer breed with eachother that point down teh line refer to them as different, they will no longer interact with eacother

remember speciation is defined as: Speciation is how a new kind of plant or animal species is created. Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics.

the formation of new and distinct species in the course of evolution.

Question 40

r-selection

Answer 40

Evolution yields two evolutionary strategies for species

When environment is far from its carrying capacity, less competition for resources. Some organsims are r-selectd some are k-selected species

Evolution will favor “r-selected” organisms

r-selected species have: many offspring, rapid development, little parental care, small body size, short lifespan, high mortality (e.g., insects, amphibians) THINK INSECTS, have lots of offspring develop rapdily with very little interaction help from parents, strategy is to put lots and lots of offspring out in world and let them go

When environment is near or at carrying capacity, more competition for resources

Question 41

k-selection

Answer 41

Evolution will favor “K-selected” organisms

K-selected species have: few offspring, long gestation, more parental care, larger body size, longer lifespan, lower mortality (e.g., humans, primates)

Very few offspsring, large gestational period, don’t die as much can see how the lists go together, how having many offpsring without much invcestment in them versus few offspring with high investment is another strategy

With few offspring makes sense those offspring would be larger, live longer better cared for, see organisms that adopt one or the other of these approaches

Question 42

Divergent evolution

Answer 42

Divergent evolution is evolution of two species away from a common ancestor

Divergent evolution = adaptive radiation

Homologous anatomical structures have a common evolutionary origin

Example: dog foreleg, human arm, whale front flipper

Implies common ancestor or common ancestor structure, can identify homolgous structures that A and B have, big example of this some ancestoral structure gives rise to forearm of human, front flipper of whale, wing of a bat, all of those are derived from a common ancestoral structure adnd they are called homoglous structures** they have a common ancestor* but the structures have different functions in present like whale front flipper for swimming, dog foreleg for running, bat for flyign but homolgous come from common acnestoral structure

Question 43

convergent evolution

Answer 43

Convergent or parallel evolution

Unrelated organisms may evolve similar anatomical structures

Structures can arise in parallel = more than once, in different evolutionary lines

Similar structures that evolve from different ancestors = analogous

Example: bird wing, insect wing

NO homolgous strucrures because no common ancestor, but get insect wing and bat wing not both derived from acnestoral wing, just that being able to fly which is a HUGE advntage from evolutionary poitn of veiw so tehy are analgous same function in present but do not imply an evolutionary relationship

Question 44

adaptive raditation

Answer 44

common acnestor derived homologous structures for divergent evolution

ex. darwin finches all started on mainland, adapted to other islands once flew out differnt beaks became differnt from eachother that is another example of adaptive radiation all started on mainland and then the finches moved out to island all adapted*

Question 45

Molecular evolution and relatedness

Answer 45

know all life forms use the same genetic code! and there are some genes that are highly conserved, i fyou want to make inferences about how closely realted differnt organisms are or different species are the best thing to do is look at how much dna they have in common, how much sequence is in common

Question 46

Molecular evolution and relatedness 2

Answer 46

Evidence for evolution is present in fossils and DNA

Fossils provide evidence of anatomical relatedness and alterations over time

DNA sequence data indicates genetic similarity of species

All life forms share universal genetic code

Genetic code evolved once, was conserved (maintained) in all life forms

Sequence and function of many genes is also conserved across species

Key genes are highly conserved and do not change much over evolution

Evolutionary distance is indicated by degree of sequence homology

More evolutionarily distant = more sequence changes

Assumes mutation rate is generally constant

“Horizontal” swap of DNA among species can complicate evolutionary trees

Question 47

Ontogeny

Answer 47

Ontogeny = embryonic development

when embryo developing goes through all evolutionary stages, not always true when human embryo is developing not fast fowarding through all of human evolution going through phase reflecting lower animals, but it is true human has tail for a while so there are other less advanced evolutionary forms that embryos do go through, cornel of truth to this not strictly true but lot can see about evolution when look at embryos

Homologous structures look really similar when preparing embyos

Question 48

ontogeny and phylogeny

Answer 48

Ontogeny = embryonic development

Phylogeny = evolutionary development of a species

During development, embryo passes through developmental stages

Developmental stages resemble evolutionary predecessors

Anatomical structures shared by related species tend to develop earlier

Example: backbone in fish and mouse

Homologous structures look similar in embryo

Anatomical structure specific to one species tend to develop later

Example: human cerebrum

Anatomical structures that are lost during evolution are lost later during development

Example: leg bones in snakes and whales

Anatomical evolution generally occurs by modifications of developmental plan

Changes in DNA affect morphology of embryo and its development

Question 49

Vestigial structures

Answer 49

Structures that serve no purpose!

Vestigial structures/organs serve no obvious or useful function = evolutionary relic

Related to useful structures in other species

Indicative of common ancestry, followed by evolutionary specialization

Human coccyx, appendix, snake limb bones, eyes of blind cave-dwelling fish

Like snakes have limb bones but obviously do nto need those and dont’ walk but can see verstiage of evolutionary history, some fish live in really dark vaces still have eyes because evolved from fish that dif have vision*

Question 50

Chordates

Answer 50

we are in phylum chordata, we are chordates which includes all vertebreates

Chordates have four basic features:

Notochord* remember only for a little while as embryos, mesodermal structure gives rise to neural tube that gives rise to brain and spinal cord, some features common to all chordates are only present in embryo; part of being a chordate*

Dorsal nerve cord (dorsal to notochord) dorsal= back

Pharyngeal pouches/gill grooves (in land animals, lost during embryogenesis) somethign have briefly in embryos which we do not have after

Post-anal tail: extension of notochord, lost in humans and frogs; humans lost tail, purely found in embryos, stil qualifies us as chordates

Within phylum of chordates all vertebrates are included

In contrast, arthropods (insects, crustaceans), annelids (worms) have ventral nerve cord

Question 51

Vertebrates classes

Answer 51

Animals are either invertebrates or vertebrates

Invertebrates lack a backbone (e.g., sponge, fruit fly)

Vertebrates have a backbone (e.g., humans, mice, crocodile)

Main classes are fish, amphibians, reptiles, birds, and mammals

Warm blooded organisms can actively regulate body temperature = birds, mammals, if we go somewhere really cold do not just equilibirate with environment we are able to regulate

Cold blooded organisms cannot regulate body temperature = fish, reptiles, amphibians

Temperature of cold-blooded organisms dictated/controlled by surroundings

On a hot day, lizard sits in shade to cool off

Question 52

Relations of vertebrate classes

Answer 52

Fish were the first vertebrates

Fish have 2-chambered heart (one atrium, one ventricle)

Amphibians evolved from fish, are able to breathe air w/ lungs, but still inhabit water

Amphibians have 3-chambered heart (two atrium, one ventricle)

Reptiles evolved from amphibians, live mainly on dry land

Reptiles have 3-chambered heart (two atrium, one partially divided ventricle)

Birds thought to have evolved from reptiles

Birds have 4-chambered heart, are warm-blooded

Mammals thought to have evolved from reptiles

Mammals are warm-blooded, have 4-chambered heart, mammary glands for nursing

Question 53

Origin of life

Answer 53

idea very early atmosphere had no molecular oxygen, water present so oxygen in water; ammonia present, so idea is that the high energy lightenign storm UV light bombarding early atmosphere jolted all these inorganic moelcules ttogether to form orgnaic moelcules amino acids and nucleotides of RNA

All current life forms are genetically similar

Life probably evolved only once, from simple chemical molecules

Early earth: no oxygen, but simple organic molecules and energy

Miller experiment: inorganic molecules + energy → organic molecules, took ammonia and water zapped them like crzy and showed yes randoly can get organic molecules and amino acids from doing that

So the idea is that the first “organisms” ppl with reproduction would have been squiggles of rna becuase can act as catalyst for interactions, code information, squiggle with RNA genome, can reproduce itself, self replicaitng RNA may have been earliest life form some ppl refer to RNA world as world of rna squiggles

Water, ammonia, methane, hydrogen + spark → amino acids, nucleotides

Question 54

Origin of Life 2

Answer 54

After chemical evolution, possibly and RNA world

RNA can be a catalyst, RNA can encode information

Self-replicating RNA may have been earliest “life form”

After RNA world → eventually organisms

Eventually dna developed from RNA, and cells evolved from that point on life was DNA based

Last common ancestor is theoretical ancestor to all present life forms

First cells were anaerobes, then photosynthetic autotrophs → oxygen

Once photosynthetic autotrophs evolved suddenly oxygen in atmosphere, once there was oxygen heterogrphs many animals were able to develop from there

know the order this happens:

inorganic molecules– organic molecules–> RNA–> DNA–> photosyunthetic autotrophs–> heterotrophs

the inorganic source of carbon peope thing of is methane**** organic molecules can think of as amino acids

Question 55

Taxonomy

Answer 55

King KINGDOM- broadest

Phillip PHYLUM

Came CLASS

Over ORDER

From FAMILY

German GENUS e.g. Homo

Soil SPECIES e.g. sapiens

So when we say homo sapiens, homo is our genus sapeins is our species

how they test- if two organisms are in the same genus, they must also be in the same family, order*** SAME EVERYTHING ABOVE BUT NOT BELOW*** so not same species

same class, same phylum, but not same order family genus species

Question 56

Types of selection graphs

Answer 56

Question 57

Converging versus diverging evolution graph

Answer 57