Evolution Flashcards
What 4 scientists are associated with the discovery of evolution?
Duffon, Cuvier, Lamarck and Darwin
what are the 3 conditions of evolution by natural selection?
- heritable characters
- characters show variation between individuals
- differential fitness (survival allowing for reproduction)
Define evolution
genetic change over time (change in allele frequencies) in a population
is all evolution caused by natural selection?
no
What do you call species dividing and changing?
speciation
what force consistently produces adaptations?
natural selection
what are the 5 pieces of evidence for evolution?
- fossils
- imperfection
- bio-geography
- molecular genetics
- natural selection in action
what defines geological periods?
mass extinctions e.g. dinosaurs by asteroid
How can fossils of trilobites show evolution?
they became extinct around 250 million years ago. Fossils of these creatures show clear signs of evolutionary change in the species over 3 million years (relatively quick in evolutionary terms)
Give an example of unintelligent design?
the appendix in humans
Give an example of natural selection in action..
peppered moths in the industrial revolution
What’s the sole carrier of genetic material?
DNA
What is meant by the DNA code being universal?
it has the same cellular machinery for decoding and copying genetic information
What can looking at DNA of different organisms show?
a common ancestor
What are molecular clocks?
a technique that pairs species compared for the same protein coding
what’s molecular phylogenetics?
looking at molecules and the genes that code for them
What has molecular phylogenetics supported?
morphological data (anatomy/physiology)
What is neutral theory?
the idea that genetic code is redundant (some mutations in genetic code won’t change the amino acid chain therefore won’t change any phenotypes)
Give 2 definitions of life..
any 2 from
- the flow of matter, energy and information
- where homeostasis occurs
- localised negative entropy (order as opposed to disorder)
- MRSGREN
How old is earth?
4 billion years old
How was the earth created?
bombardment bringing water and destruction
How was the young sun different?
higher UV levels- more UV on the earth’s surface
When did life first appear?
3.8 billion years ago
What’s the most likely way life first appeared?
In the deep sea at alkaline hydrothermal units where alkaline and acidic water meet, allowing the protons giving energy to fuel the first replicating molecules from these proton gradients
What did the first sources of life use as genetic material?
RNA
Draw a flow-chart showing how life’s form changed
complex molecules from random chemistry –> RNA –> Proteins –> DNA
when did amino acids first start being incorporated into life?
after the RNA world
what is LUCA
Last Universal Common Ancestor
What’s more fragile DNA or RNA?
RNA
why did cells first form?
DNA needed protection as it’s fragile
What is normally needed for life to exsist? (4)
- cool temperatures
- water
- gravity
- protection from radiation
When did the great oxidation event occur on earth?
around 2.5 billion years ago
What’s the theory of the cause of the great oxidation event?
the first prokaryotes were producing methane and cyanobacteria were producing oxygen, which the methanogenic bacteria were consuming. some event caused a mass death of methogenic bacteria and oxygen producing bacteria dominate
What are the main cellular features of eukaryotes? (4)
- nucleus
- mitochondria
- choroplast (in plants)
- golgi bodies
What do eukaryotes have that prokaryotes don’t?
membrane-bound organelles
What’s bigger pro or eukaryotes?
Eukaryotes
are some eukaryotes multicellular?
yes
when did eukaryogenesis happen? How many times?
26 billion years ago. once
How did eukaryogenesis probably occur?
an archaebacterium engulfing heterotrophic eubacteria (eubacteria eventually became mitochondria)
Are mitochondria a product of natural selection?
no (they appeared as a chance event)
What’s the Cambrian explosion?
The sudden appearance of several fossils from the same time period
Give an example of animals that came from the cambrian era..
arthropods, chordates and worms
Why did the cambrian explosion happen?
A physiological change in organisms led to dissolved oxygen levels allowing for an active lifestyle. Geographical change with new seas and new niches. There was a geochemical change when sea levels changed allowing an abundance of trace metals to make exoskeletons
How long ago were the dinosaurs wiped out?
66 million years
what did the disappearance of the dinosaurs allow?
other large reptiles, mammals and birds had ecological space to evole
how long do ecosystems generally take to recover from mass extinction?
20 million years
define a species..
A population of reproducing organisms that is isolated from other populations
Why is the definition of a species not all-encompassing?
it doesn’t work for prokaryotes and eukaryotes that don’t strictly reproduce sexually. It also can’t be used when looking at fossils of extinct species or for bacteria/archaea
simply, what is allopatric speciation?
speciation due to Geographical isolation (allo- other, patric- homeland)
what’s the typical mode of speciation?
allopatric
What’s directional selection?
where the population gradually changes due to a selection pressure to favour a single ‘extreme’ phenotype
What’s distruptive selection?
where the 2 extreme (most different/ opposite) phenotypes are favoured over the intermediate one
What’s stabilizing selection?
where the intermediate/’middle’ phenotype is favoured over the either ‘extreme’ phenotypes
What’s genetic drift?
where the variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce
why is genetic drift unlikely to happen in large, randomly mating populations?
they have low chances of large fluctuations and more of each allele
What are founder effects/ bottlenecks?
when there’s reduced genetic diversity due to a population being descended from a small number of colonising ancestors
what is sympatric speciation?
speciation which occurs when the new and old species are living in the same geographical location (sym-same, patra- homeland)
what clearly shows sympatric speciation
plants can show polyploid speciation
what’s the mean time for speciation to occur?
5 million years
why is isolation key for speciation?
it prevents gene flow between the populations
what are prezygotic barriers?
a mechanism that prevents reproduction pre-mating
give 2 examples of prezygotic barriers?
2 from:
- different habitat locations
- temporal isolation (breeding/mating at different times)
- behavioural isolation e.g. differences in mating/courtship behaviour
What are postzygotic barriers?
a mechanism that prevents reproduction after or during mating
give 2 examples of postzygotic barriers..
any 2 from:
- mechanical isolation (physically cannot mate)
- genetic isolation- gametes don’t ‘work’ together
- infertile hybrids
What’s microevolution?
changes in the gene pool of an organism over time
what’s a gene pool?
all the alleles of all the genes in the individuals of a population
What’s macroevolution?
evolution of a grand scale
what 2 factors are required for evolution by natural selection?
1) differential reproductive success
2) differences between organisms
What was darwin’s main issue?
he came up with the theory of evolution, however he did not have a mechanism for it
who first began to give explanations of how genes pass from one generation to the next (inheritence)?
gregor mendel
what is the study of microevolution called?
population genetics
What 5 things can population genetics tell us?
1) how human pathogens are evolving e.g. bacteria which are antibiotic resistant like MRSA
2) How humans have evolved in response to pathogens
3) how much genetic diversity is present in a population
4) genetic structure of a population
5) response of population to change e.g. climate change
How does population genetics study gene pools?
by looking at a gene locus model (it’s impractical to study a whole population)
How does one measure the allele frequency and genotype frequency?
number of one type of allele/ total number of alleles (double the number of organisms if the organism is diploid)
what’s the equation for when allele frequencies reach an equilibrium?- what do the symbols stand for?
p2+2pq+q2=1- The Hardy- Weinberg equation
p2- RR homozygotes
2pq- Rr heterozygotes
q2- rr homozygotes
If an equilibrium is reached in alleles, it will stay the same if which 5 factors exist?
- population size is large
- mating is random
- no migration from other populations
- no selection
- no mutation
What 4 factors change allele frequency?
- genetic drift (in small populations)
- non- random mating
- migration
- selection
What’s neutral theory?
many alleles are selectively neutral and their frequencies will fluctuate randomly over time
What’s selection theory?
the idea that the selection of combinations of traits in an organism trade-off between quantity and quality of offspring
How many base pairs do humans have?
3x10^9
what percent of all the human base pairs code for proteins?
3
what percent of our base pairs are regulatory genes?
10%
what percent of our base pairs are remnants of transposons?
45
what are transposons?
parts of DNA which move around, may be remnants from a viral infection
what percent of our base pairs are ‘junk’?
85
what is ‘junk’ DNA?
DNA which if deleted would have no effect on fitness
how much do humans differ in DNA from eachother?
by 0.1% (trivial amount- could relate to altruism)- most these differences are in junk DNA
what percent of our DNA is from retroviruses?
8
are we still evolving?
yes
give one piece of evidence that shows humans are still evolving..
1 of:
- a study of 50 tibetans who live at 4000m altitude (where there’s 40% less oxygen), who have lived there for 2750 years were compared with Han chinese people who live there too but migrated more recently. scientists found that the gene EPAS1 (that controls blood cell production) is mutated in 87% of the tibetans but only 9% of han chinese.
- genetic difference found in bajau people who dive for long periods while holding their breath. this genetic difference allows them to hold their breath longer
where’s the largest genetic variation in humans seen?
africa
what happens to genetic variation as you get further away from Africa?
it reduces
why does genetic variation reduce the further from africa you go?
as humans migrated, the gene pools reduced as smaller groups were travelling far away
In how many waves did humans leave africa?
2
when were the 2 waves of humans leaving africa?
the first was 100,000 years ago the second was 60,000 years ago
what happened during the first wave of humans leaving africa?
they migrated to china, however died out as they have no living descendants
what happened during the second wave of humans leaving africa?
they succeeded in colonising the rest of the world
what was found when looking at 6 genomes from all over the world?
there was a bottleneck 70,000 years ago where the entirety of the human population was composed of 12000 individuals who we all descend from
why did the bottleneck 70,000 years ago happen?
may be due to climate change
at what sort of rate did humans travel out of africa?
around 1km per year (very gradually)
How were neanderthals physically different?- give 3
any 3 from:
- more prominent brow
- larger teeth
- shorter
- broader
- physically stronger
where did neanderthals live?
in large areas around the world
when did homosapiens overlap with neanderthals?
5000 years ago
are neanderthals our direct ancestors?
No- our cousins
were neanderthals intelligent?
more so than previously though
where did the last group of neanderthals live?
Gibraltar
what was found found when the neanderthal genome was sequenced in 2010?
non-african homosapiens interbred with neanderthals, therefore by the biological definition of species, we’re not a different species
around 3% of homosapien non-african DNA is neanderthal
How were denisovans discovered?
In 2011 from teeth that weren’t ours or neanderthal- more artefacts of them have been found since
did homosapiens mate with denisovans?
yes
are we or neanderthals more closely related to denisovans?
neanderthals
how do denisovans and tibetans link?
the EPAS1 genes tibetans living at high altitude have is beleieved to be from denisovans
were denisovans and neanderthals mating?
yes- hybrids were found
what’s different about homosapiens to other human species?
- we have a history of art e.g. cave wall art
- we invented many tools
- there’s a correlation between humans arriving in different areas worldwide and species of megafauna (large animals) becoming extinct
define fitness.
the relative probability of survival and reproduction of a given genotype
is fitness easy to calculate precisely?
no
what affects survival and reproduction?
environmental conditions (which change in time and space e.g. dinosaurs fit until meteor strike)
can fitness come down to a single allele?
no
how is the sickle cell allele driven survival?
those who are heterozygous for the disease aren’t affected by malaria- making this advantgeous in parts of africa but not europe or america (unfit alleles are sometimes preserved)
what is evolution?
change in allele frequency
are phenotypes and genotypes always directly linked? why?
no. because environmental factors can affect phenotypes
are species selected?
no, individuals within the species are
What’s Runaway sexual selection?
The idea that certain traits (usually in males) are preferable to females e.g. large peacock tails, to the point where the genes for these are passed down, as the trait increases reproduction likelihood e.g. the peacock tail size increases
Why can runaway sexual selection only exist up to a point?
because eventually the trait change can be maladaptive e.g. large peacock tail means more likely to be killed by predators
What are most social insects (sexually)?
sterile- only the queen reproduces
What affects who will be the queen in social insects?
environmental factors
How do insects act?
Altruistically
What did Bill Hamilton study?
Altruistic species
What’s Hamilton’s rule?
The evolutionary strategy that favours the reproductive success of the organisms relatives/species, even at the cost of the organisms own survival/reproduction
Is there likely to be a gene for altruism?
no
What could Hamilton’s rule explain about humans?
the widespread prevalence of altruism in the human world
where are the Galapagos islands?
approx. 1000km from the coast of Ecuador
What separates the Galapagos islands from S.America?
deep water
The fact that deep water separates the Galapagos islands and S.America means that…
terrestrial species on the islands won’t have many relatives nearby, neighbouring islands will have a few close relatives
there’s very little gene flow between the islands and mainland
When did charles darwin explore the galapagos islands?
1835
What’s an endemic species?
A species only found in one habitat e.g. galapagos finches are endemic to these islands
what did Darwin notice about the galapagos finches?
the shape of the bill (beak) of each species was adapted to its particular ecology
what did peter and rosemary grant do?
studied the galapagos finches for the past 30 years
What was the first stage of evolution of the eye?
an isolated photoreceptor allows an animal to monitor the intensity of ambient light
what was the second stage of evolution of the eye?
animals can tell where the light is coming from- photoreceptors gain a shield giving the owner a pixel sense of the world (allows animal to move towards or away from light source)
What was the third stage of evolution of the eye?
shielded photoreceptors cluster in groups, each pointing in a slightly different direction, allows the integration of different information, at this point photoreceptors become eyes
what was the fourth stage of evolution of the eye?
lenses are added to allow focusing of the light- vision becomes sharp and detailed
what did Ernst Mayr claim about the origins of eyes?
they had 40-65 independent origins
what did walter gehring argue about the evolution of the eye? and why?
that they evolved just once- after he discovered that the same master gene (pax6) controls eye development in virtually every creature with eyes
who was right about eyes mayr or gehring?
both partially
what are eyes all made up of?
- opsins
- lenses
- retinas
- bundled nerve fibres
sympatric speciation that involves a hybrid between 2 related species is known as?
an allopolyploid
