Unit 9 - How we Evolve Flashcards
1
Q
Evolution and Ecology
A
ecology and evolution help us understand biodiversity and how it is maintained over time
2
Q
Biological Evolution
A
heritable change in a population across many generations
small scale - change in a single gene (microevolution)
large scale - change above the species level (macroevolution)
*macroevolution - process that gives rise to different species
2
Q
Why Study Evolution
A
we need to know how organisms interact with each other and the environment
**evolution tells us the history and diversity of life (we are all related!!!) - we all have a common ancestor
3
Q
Evolution Constant Process
A
- changes take place all around us
ex: bacteria can develop resistance to antibiotics
4
Q
Divine Creation
A
species are permanent and life is unchanging
5
Q
Plato
A
he thought every organism was created by god and was perfect
- types were unchanging
- because organisms were created by God, the species couldn’t change
6
Q
Aristotle
A
he thought organisms weren’t changing but put them in a heiarchy
scala naturae - he made a heiarchy from imperfect organisms to perfect organisms (once placed in the hiearchy there was no movement to move on it)
7
Q
Fossils
A
fossils indicate that there is change over time
- noticed that fossils are found in some layers of sentiment but not in others
- the shallower layers of earth = younger fossils
- the deeper layers of earth = older species
8
Q
Catastrophism
A
the idea that major disturbances cause change
- a very big thing has to happen to cause change
- Georges Cuvier thought this
- didn’t think species could change over time
- he thought organisms were coming in from other places because of a catastrophic event
9
Q
Uniformitarianism
A
gradual changes over time happen because of natural processes
- small changes build up and cause a change (ex: creation of rivers)
- Charles Lyell thought this
- thought that the same processes that occured in the past occur at the same rate today
*this doesn’t make sense bc it took thousands of years to make rivers
9
Q
Lamark
A
he thought that life evolves which is why we have fossils (species change over time)
- lamark was the first to propose a system that explains how life changes over time
the system: Inheritance of acquired characteristics
ex: giraffes have long necks
- he thought the necks had to be stretched to get a longer neck so they can reach for food
**this system isn’t right
10
Q
Darwin’s Treck
A
the British Gov. sponsored his trip to map out the coast of South America
- called the voyage of HMS Beagle
- he spent a lot of time on land near South America
11
Q
Darwin Fossils
A
fossils looked like South American organisms that are still living
extinct = not living
extant = modern day, currently living
endemic species = species unique to a defined geographic location
- the species ins’t found anywhere else in the world (ex: plants and flowers in Hawaii)
- the species also couldn’t have migrated to get there
-
12
Q
Organisms in Temperate Regions of South America
A
organisms in temparate regions of South America were more similar to organisms in tropical areas of South America and not like organisms in other temparate regions of Europe
ex: Chinchilla and Mara both live in different areas of South America
- they have differences but also shared similarities
13
Q
Life is Diverse
A
ex: all the islands have turtles
- some have long necks and some have short necks
- their neck length depended on what kind of food they ate which depended on the island
the animals that lived on the island at the time weren’t scared of humans because they had evolved there for so long without human contact
14
Q
Darwin’s Finches
A
the finches on the Galapagos islands looked like the mainland finches but there were multiple types
(the finches on the island were different than the finches on the mainland)
- the bill shape is an adaptation to different means of food gathering
- galapagos finch species varied by nesting size, beak size, and eating habits
*the beak sizes depended on what kind of food they were eating
15
Q
Animals on Mainlands Vs. Islands
A
they were similar to each other but has some important differences
***the species developed on the mainland and then moved to the islands (maybe bc of a storm)
ex: the island iguana has hands that can grip trees better vs. the mainland inguana has softer hands bc the trees are softer
***the island species originally came from the mainland and then adapted to their new island life (which is why they have differences)
16
Q
Darwin’s Evolution Idea
A
his idea for how evolution worked was influenced by Malthus’ ideas
- producing more offspring that can survive creates a competitive enviornment for siblings
- variation among siblings would make some individuals have a slightly higher chance of survival (some people are more fit than others)
17
Q
Wallace
A
developed his own theory of natural selection as Darwin did
- thought species today came from ancestral species (we are descendents of ancestors that have developed over time)
- natural selection is what causes changes in a species over time
natural selection – the trait that gives people advanatges to survive develop over time
18
Q
Genetic Variation
A
there’s variation among individuals within a species
sources of genetic variation:
- mutation (creates new alleles - this happens through reproduction)
Sexual Reproduction – creates new combos of alleles (they can be passed on to the next generations)
ex: we can breed plants to have more leaves (desirable trait)
- variation is heritable (has to be sent on to the next generation)
19
Q
Organisms and Offspring
A
organisms can produce more offspring than the environment can support
- competition happens between individuals
- many offspring can’t survive and reproduce
- individuals whose inherited traits give them higher probability of surviving and reproducing in an environment tend to have more offspring than other people
(they have higher fitness!!!)
fitness = ability of an organism to survive and reproduce, passing their genes down
20
Q
Accumalation of Favorable Traits
A
differences in the ability of individuals to survive and then reproduce leads to the accumulation of favorable traits in population over generations
- the increasing frequency of favored traits in a population leads to evolution
ex: the population is green and brown beetles
- the bird likes the green beetles over the brown beetles
- over time, more beetles are brown
- eventually, only brown beetles left bc it’s advantageous to be brown so you don’t get eaten
20
Q
Natural Selection
A
the differential survival and reproduction of individuals because of differences in traits
- because individuals with certain variants of a trait tend to survive and reproduce more than individuals with less successful variants, the population evolves
***populations evolve over time
***doesn’t make perfect organisms
- natural selection doesn’t work toward a goal, it just modifies traits that are already present
20
Q
Fitness
A
fitness = the ability of an organism to pass its genes to the next generation
- includes surviving, finding a mate, producing offspring
- fitness depends on the enviornment that the organism lives in
- fitness can change if there’s a change in the environment
ex: if there’s a lot more green plants, green beetles can hide better so the green trait is advantageous, not the brown
20
Natural Selection at Work Example
ex: mice population
- 30% of population - pale yellow
- yellow mice are easy to see (this is not fit)
No yellow mice - eventually all of the yellow mice cats were removed from the populations
yellow mice found --- they came back after the cats were removed (they had the yellow coloring in their recessive allele) -- happened bc of a change in the environment
20
Variation
an allele, trait, phenotype (whatever) is required for natural selection act upon
- if there's no variation within a population, natural selection can't work because it wouldn't give anyone an advantageous trait
- not all genetic variation has natural selection act upon it (there can be neutral variation - no effect)
ex: fingerprints are all different - no fingerprint is more advantageous that another one
***not all genetic variation makes an organism more fit (increased chance of survival and reproduction)
20
Artificial Selection
selective breeding
- selecting specific traits across generation on purpose to get a desired result
ex: pugs
- they used to have normal noses but humans liked the look of the flat nose so now they all have flat noses
- the nose was artificially selected for
ex: corn
- they kept artifically selecting it for more cornels and taller stalks
20
Darwin & Artificial Selection
he knew that artificial selection would cause the traits to be passed on to future generations (ex: the pugs now all have flat noses and that keeps getting passed on)
- he loved pigeons (their feather direction was selected for)
**Mutations can control the direction of feather growth (the trait can be selected for or against)
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Homologous Structures
features that are made with similar construction due to common ancestry but function differently
- some ancient structure became modified in different ways over time
(to suit the organism and what is advantageous for them)
- the form and function of the structure depends on the species' lifestyle and environment
ex: humans have arms and whales have flippers
- we all have flanges but they serve a different structure for the needs of the environment
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Homologous Structures -- Ancestry
the animals that all have the homologous structure share a common ancestor who had all of these shared traits
- the ancestor is more distant if they are really different from the organism
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Vestigial Structures
anatomical features with no function
- they organism has the feature because it looks like the same feature that the ancestor had
ex: whales and snakes have small femurs (leg bones) that don't do anything because they don't have legs
- they have them because their anscetor had a femur and used it
ex: fish with eyes that don't work (the fish doesn't need sight for their environment)
- the anscestor needed sight which is why they have the eyes
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Molecular Homologies
similar molecule composition of proteins, DNA
***related species have greater similarity in DNA and proteins that unrelated species
ex: humans and monkeys share a lot of similar amino acids
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Embryonic Homologies
similarities in embryonic life stage across species
- the developmental similarities are because of a common ancestor
- embryonic homologies happen because of molecular homologies (shared genetic code)
ex: snake, chicken, human all look similar as embryos but when they develop more they look very different
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Analogous Structures
similar structures (with the same purpose) among different species but they don't have a shared common ancestor
- these structures evolved independently to serve the same purpose
ex: bats and butterflies common ancestor doesn't have wings
- they developed wings for flight independently
***analogous sturctures happen because of convergent evolution
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Convergent Evolution
evolution of similar structures in distantly related organisms that live in similar environments
ex: butterfly and bat
ex: the fins of turtles and whales are analogous
- they have similar structure with the same purpose (to swim) but their common ancestor didn't have fins
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Carcinization
example of convergent evolution
- when non-crab organisms develop a crab-like body structure (body plan)
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Biogeography
geographic distribution of species
- the similarities between species separated by distance or barriers (ex: ocean)
- their common ancestor was when the continents were together
- evolutionary changes happened once the continents split (ocean separates them)
ex: fishes
- the fish are all related but they live far apart because they are restricted to fresh water (can't get to each other by ocean)
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Biogeography species similarities
species on ocean islands tend to resemble species of the nearest mainland (even if the environment is different)
- species on ocean islands don't resemble species on islands with similar environments in different parts of the world
ex: species in island off western Africa look like the species on mainland of western africa
- they island species doesn't look like the galapagos species
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Fossil Record
links between extinct and extant species
- similarities between fossils of extinct species and modern extant species (but they do have differences)
ex: fossil of huge turtle (15 feet)
- now turtles are less than 7ft long
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linking Biogeography and the Fossil Record
Pangea -- continents were all connected (huge land mass)
- after Pangea, identical fossils were found in different parts of the world because they separated and they were isolated and evolved over time
-
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Natural Selection Order
variation in heritable traits within a population (needs to be there so natural selection can act)
- then natural selection causes differences in survival and reproduction
- this difference changes traits in a population over time (ex: now only green beetles)
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Population
indiviudals from the same species that can breed with each other and make fertile offspring
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Microevolution
generation-to-generation change in allele frequencies in a population
this causes: changes in a gene pool (all of the alleles in a population)
ex: original population is split 50/50 between red and gray horses
- bc of microevolution, over time the population because 20% gray and 80% red
**a change in allele frequency over time means that a population has evolved
36
Genetic Drift
random events that cause allele frequencies to change unpredictably from one generation to the next
- this doesn't mean an allele was more advantageous, just because of random chance
ex: an earthquake wipes out a lot of horses -- randomly your left with more gray horses
***this is really important in small populations
- genetic drift can really reduce or even eliminate alleles within a population
ex: could be left with 0 red horses
37
Fixed Allele
this happens in genetic drift
fixed allele = when only 1 allele of a gene remains in a population
ex: landslide happened so only gg individuals left (brown)
- the g allele = fixed allele
- no there's no variation within the population, so no individual has an advantage or disadvantage over another one
- natural selection can't act on this population bc there's no variation
38
Genetic Drift: Founder Effect
when individuals are isolated from the main population
- the founding population (new population) doesn't represent the gene pool of the original population
- within the founding population:
- there can be a loss of alleles
- can be an increase in frequency of alleles that were rare in the original population
ex: the original population had more red horse than gray
- now in the founding population, there's more gray horses than red
39
Founder Effect Human Example
in an island in the South Pacific, 15 people founded it
- one colonists had a recessive allele for blindness
- over time, the population increased, and the gene with the disease spread
- much more people on the island have the allele (increase allele frequency) than in other parts of the world because one of the founders had the allele
40
Genetic Drift: Bottleneck Effect
the population goes through a period when it's size decreases
- lots of individuals and their alleles are lost
- the population size later increases
- but the genetic diversity is still low (can either eliminate an allele or make it the allele frequency different)
ex: population with blue and yellow alleles
- bottleneck effect happens (population looses yellow allele)
- population grows again but there's still no yellow allele (so the genetic diversity is low)
ex: population with blue and yellow alleles
- after bottleneck effect and the population increases again, there's still blue and yellow alleles but now there's a lot more blue alleles
41
Gene Flow
genetic exchange happens because of the migration of fertile individuals or gametes between populations
ex: the fertile individuals migrate to a population of horses and chance the allele frequency in the population they migrated to
**decreases differences between populations
***increases genetic diversity within a population
***can increase or decrease the fitness of the receiving population
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Gene Flow Beetle Example
2 populations of beetles (one green and one brown)
- a brown beetle migrates to a green population and over time, as they beetles breed and reproduce, the population is now becoming more similar to the brown population than the green population
- population is now brown and green
43
Gene Flow Can Decrease the Fitness of a Population
ex: Bentgrass
- the bent grass near a copper mine had alleles that built up the tolorence to copper
- because of the wind, some bent grass migrated into other areas far away from copper mines which caused them to have alleles with copper tolorence
- having alleles with copper tolorence was harmful to them (decreased their fitness)
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Gene Flow can Increase the Fitness of a Population
ex: insecticides to control mosquitos that carry disease
- over time, the mosquitos developed a resistance to the insecticides
- the population is now resistant to insecticides so they can survive it and continue to reproduce
- because of gene flow, they shared this allele with new populations
- natural selection favors the gene that is resistant to insecticides (so the allele will be maintained over time)
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Gene Flow can Maintain alleles that are disadvantageous
snakes on the mainland have to stripes because it was adaptive
- some snakes on the island had stripes too even though it was a disadvatnage to have stripes
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Mutation
bring new variations into populations
- a random change in the DNA sequence
point mutation --- change in a single nucleotide base pair
ex: Sickle Cell Anemia
mutations can be caused by errors in the DNA replication, radiation, or chemicals
changes must be heritable for evolution to occur (the changes have to be passed down to offspring)
ex: mutation in coat color had to be passed down to offspring
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Good Mutations
some mutations are good (they give an advantage to survival or reproduction)
**they have a higher chance of remaining in the population
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Bad Mutations
some mutations are bad (they give a disadvantage to survival and reproduction)
***mutations are more often bad than good
- organisms are usually well-suited for their environments (so the mutation makes it worse)
**they usually get removed fast through natural selection
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Neutral Variations
when there's no advantage or disadvantage from a mutation
***most mutations are neutral bc:
- non-coding regions of DNA (introns) if there's a mutation on an intron it gets cut out so it doesn't matter
- no change in amino acid sequence (the same protein will be made so it doesn't matter)
50
Directional Selection
favors individuals at one extreme of a phenotypic distribution
- individuals at one extreme of a trait experience poor reproductive success
ex: body size
- best to have one extreme (lets say it's best to have big body size)
- the individuals with bigger body sizes are more fit
- over time, all of the individuals get closer to a bigger body size because it's more fit
*think about the curve, the curve gets narrower and moves towards one extreme
51
Disruptive Selection
favors individuals with either extreme phenotypes
- the people in the middle are disadvantaged (have poor reproductive success)
- over time, there will be fewer individuals in the middle
ex: birds with small beaks are advatanged to eat soft seeds and big beaks are advantaged to eat hard seeds
- the birds with medium beaks are disadvantaged
52
Stabilizing Selection
favors individuals with the intermediate phenotypes
- good to be in the middle
*this reduces the variation of a trait within the population
- natural selection is removing the extreme traits because it's selecting for the intermediate trait
ex: big dogs sink into snow
- small dogs are too weak to survive
- medium dogs are strong enough to survive and won't sink into the snow so they're the most advanatged
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Balancing Selection: Frequency Dependent Selection
maintains genetic diversity in the population
- frequency-dependent selection --- the fitness of a phenotype depends on how common it is in the population
ex: predatory fish either have right or left mouth to feed on the big fish
- the big fish learns how to defend itself from the more common fish type (left or right mouthed) until the other side becomes common
- so genetic variation is maintained
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Balancing Selection: Heterozygote Advantage
individuals who are heterozygous for an allele have greater fitness than either type of homozygote (recessive or dominant)
ex: Sickle Cell Disease
- homozygotes for this all more resistant to malaria then homozygotes
**natural selection doesn't always eliminate the weak or less fit allele
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Sexual Selection
acts on traits that affect reproductive success
- have to be able to reproduce
- just because you survive, doesn't mean you get to reproduce (pass your genes to the next generation)
- you need to find a mate, and successfully reproduce
***sexual selection favors traits that increase reproductive success (ex: male peacocks have colorful feathers)
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Tradeoff of Sexual Selection
sometimes the same traits that increase the chance of mating and reproduction (ex: bright feathers) decrease survival success
- the color makes them more visible to predators
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Intrasexual Selection
competition between individuals of the same sex (usually among the males of the species)
ex: ram
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Intersexual Selection
traits that help individuals of one sex be "chosen" by the other sex (mate choice)
ex: when the males tries to be more desireable to the females (the male peacocks have bright feathers)
intersexual selection leads to sexual dimorphism: when sexes of the same species differ in their phenotype (they look different)
ex: male peacocks have colorful feathers and female peacocks don't
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Speciation
bridge between microevolution and macroevolution
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Morphological Species Concept
a group of individuals that are similar in appearance
- it's not enough to just look at the appearance bc they might be different species
**doesn't allow for gene flow
***appearance doesn't always define a species
ex: two skunks look like each other but aren't the same species
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Biological Species Concept
a group of individuals that have the potential to interbreed and produce fertile offspring
- allows for gene flow between individuals that look different
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Limitations of Biological Species Concept
- can't work on extinct forms of life because we have no way of looking at fossils and knowing (some could be older and some could be younger)
- there might be subtle differences that are hard to see in the fossils
- doesn't work for asexual reproduction because it requires interbreeding within species (ex: bacteria)
potential to interbreed:
- if they're isolated can they breed when put together
- ring species --- gene flow occurs between neighboring populations
- at the end of the ring, the population don't interbreed
ex: over time, the individuals spread out and create new populations
- if the species come back into contact at the other side of the barrier, they might not be able to interbreed
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Reproductive Barriers
reproductive isolation:
- biological factors (barriers) block the members of two species from interbreeding
- barriers prevent gene flow and limit the formation of hybrids
- a combo of barrier can isolate a species' gene pool (they can't interbreed)
2 types:
1. pre-zygotic
2. Post-zygotic
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Pre-Zygotic Reproductive Barriers
prevent successful production of zygotes (barrier that occur before fertilization -- before the zygote forms)
- some have no mating attempted between individuals and some do attempt to mate
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Temporal Isolation
*pre-zygotic barrier - NO mating attempted
- reproduction or reproduction cycles occur at different times
- they can't mate because they're not reproductively active at the same time
ex: american toad breeds in early spring
- fowler's toad breeds in late spring
so they can't mate with each other
66
Habitat Isolation
*pre-zygotic barrier - NO mating attempted
- they have different habitat preferences or requirements for reproduction
- they can occupy the same habitats but reproduce in diff. places
ex: american toad breeds in shallow creeks
- fowler's toad breeds in big pools of water
67
Behavioral Isolation
*pre-zygotic barrier - NO mating attempted
- some behavior prevents them from attraction or mating
ex: American toad has their unique mating call
- fowler's toad has a different unique mating call
- they developed their own mating calls so the females of one species aren't attracted to the males of a different species
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Mechanical Isolation
*pre-zygotic barrier - MATING attempted
difference is structure that prevent successful mating
- they attempt to mate with each other but can't
ex: difference in genitalia
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Gametic Isolation
*pre-zygotic barrier - MATING attempted
- the gametes do not unite (they can't combine to make a zygote)
ex: plant release gametes into the water at the same time but they can't unite because they need specific recognition molecules
*gametic mismatch prevents sperm and egg from combining
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Post-Zygotic Barriers
prevent successful production of viable offspring
organisms mate and fertilize a zygote and the zygote is formed
*the zygote is formed but doesn't develop into a fertile adult
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Hybrid Inviability
*post-zygotic barrier
- the development of the zygote is impaired
- during zygote development, an issue happens where the zygote can't continue to develop (hybrid is weak)
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Hybrid Sterility
*post-zygotic barrier
- hybrid zygote develops, but can't reproduce (the zygote is infertile)
ex: horse + donkey = mule
- viable offspring but it can't reproduce
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Hybrid Breakdown
*post-zygotic barrier
- hybrid zygote develops and can reproduce offspring but the offspring later can't reproduce (the later generations after the initial kids can't reproduce)
*we see this more in plants than in animals
ex: cotton
74
Allopatric Speciation
new species arise because of a new barrier that prevents individuals from meeting up and mating with each other (over time evolutionary changes add up which is why they're now different species)
- they were separated by a geographical barrier (no gene flow)
- natural selection, genetic drift causes the population to split
*form of reproductive isolation
- places with more geographic barriers have more species
- endemic species (species that live in a limited area) are common on islands
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Sympatric Speciation
opposite of allopatric
- new species arise without a barrier
- speciation without a geographic barrier
- this means, a reproductive barrier had to evolve first (bc there's no geographic barrier)
polyploidy -- can lead to sympatric speciation (causes instant speciation event)
- a mistake happens where there's a different number of chromosomes (instantly creates a new species)
ex: lakes have 500 different species of fish
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When has speciation happened
we use fossils and molecular data to look at the time between speciation events
*this tells us that whales and dolphins most recent living common ancestor is a hippo
- we can compare the fossil record to the paleoclimate (ancient climate)
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Gradualism
slow and steady change over time
- enough different reproductive barriers that give rise to a new population
support for gradualism:
- studies of microevolution, population genetics
*speciation is usually a slow process
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Punctuated Equilibrium
periods of little change interrupted by short periods of quick change
*speciation is usually a slow process
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Adaptive Radiations
periods of time when many new species arise fast
- this usually happens when there's an ecological niche to fill:
ex: no predators left, invading an island, evolution of key body parts (jaws, surviving on land), after a mass extinction
**most adaptive radiations happen when species can spread out in the environment because their competitors aren't there (the new species can evolve to specialize in these new roles)
- key innovations from microevolution can lead the way for adaptive radiations
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Mass Extinctions
- very high right of extinction
- large lineages end (line of ancestors)
- happens because of enviornmental change (ex: ice age)
- 5 or 6 mass extinctions
*usually after a mass extinction happens, adaptive radiation happens
81
Consequences of Mass Extinctions
can have cascading effects (domino effect)
- can open up niches for new species (this is why usually adaptive radiations follow mass extinctions)
