Karteikarten
LEC 141: Evolution
Karten in diesem Stapel (131)
- 1what was the first widely accepted idea about where life comes fromit came from Aristotle (300BC) who claimed it arises from nothing
- 2who disproved the idea that life arises from nothing and how was this achievedFrancesco Redi (1668) disproved this idea with an experimental test. This involved comparing covered and uncovered meat: flies only emerged from the uncovered meat which had been visited by other flies. This shows that life only comes from previous life. Life on Earth has come to be so diverse and complex due to evolution
- 3when was the idea of natural selection first mentionedCharles Darwin (1809-82) wrote on the origin of species by means of natural selection (1859). This proposed natural selection as a mechanism for evolution. Alfred Russell Wallace (1823-1913) independently came up with the same idea and wrote a joint paper with Darwin in 1858.
- 4what are the key features of natural selectionindividual plants and animals show variation in their features
this variation is heritable so that offspring resemble their parents
there is competition because many more offspring are produced than can be maintained by resources e.g. food/space
overproduction results in competition - 5what process leads to adaption or changes in traits in a populationthere is selection; individuals live or die (survive long enough to reproduce) depending on the presence/magnitude of the trait which influences the outcome of competition
this process is called evolution and results in adaption or changes in traits within the population - 6describe Darwin's voyages to the Galapagos islandsDarwin was inspired by his own observations during the HMS beagle voyages to the Galapagos islands, especially those of finches. Darwin noticed that the finches on each island had different beaks and behaviours as they had adapted to the specific conditions (food) available to them. Darwin realised that explaining such adaptions was essential to understanding evolution. His explanation of how adaptions arise centred on natural selection, a process in which individuals which have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits
- 7who was Darwin inspired byDarwin was inspired by Thomas Malthus (1766-1834) who wrote in "Essay on the Principle of Population" (1798) that more offspring are produced than those that survive to reproductive age, this is because resources are limited, therefore there is competition for resources which leads to selection (those better able to compete for resources survive)
- 8what was one of Darwin's main problemshe lacked an explanation for the mechanism for heritability. This was explained using genetics after Darwin's death (Neo-Darwinism)
- 9what is the modern view of evolutionindividuals compete with each other, and only succeed if they reproduce themselves. Selection also acts on individuals not on species or groups.
evolution is ongoing
selection pressures vary in time and space
there is no aim and no striving to fit a niche - 10name the seven different forms of evidence for evolutiondirect experiment
biogeography
fossil record
homology
vestigial structures and homoplasy
embryology
comparative behaviour and biochemistry
hierarchal organisation of life - 11what are guppies (direct evidence from experiment)Guppies are small fish native to South America. Amongst guppy populations there is intense competition for females who prefer to mate with males with more spots. The guppy's have two main predators: Crenicichila alta is a large predator which eats adults and the Rivulus hartii is a smaller predator which eats the young guppy's
- 12where did the idea that guppy's provide evidence for evolution come from (direct evidence from experiment)not all streams and pools have predators. Pools with Crenicichila present have guppy males with fewer orange spots on average. Pools with no predators have guppy males with brighter/more orange spots. This suggests that the Crenicichila applies a selection pressure which causes males with fewer spots to survive. However, this is a correlation and not a causation.
- 13what was the experiment on guppy's (direct evidence from experiment)John Endler set up an experiment with artificial pods with a random selection of guppies which were allowed to bread. Then after 10 months predators were added. The average number of spots in males increased until the addition of predators which caused the average number of spots to decrease. This is direct evidence for evolutionary change over a short timescale. The effect of predation reduces colouration in the population through natural selection
- 14How does biogeography provide evidence for evolutionliving organisms don't occupy all there potential habitats (e.g. polar bears), but similar (yet different) organisms occur on different continents. This distribution makes sense when we consider continental drift. 250 million years ago the land mass of the Earth was organised into a super continent called Pangea. The animals living on this super continent were separated by continental drift which led to similar and closely related organisms to evolve in different ways (e.g. Ratites)
- 15how does biogeography provide evidence for evolution part 2oceanic islands have few species, many of which are endemic but resemble mainland species (e.g. marine iguana, giant tortoise). These island species may have been separated when land bridges disappeared (e.g. due to a rise in sea levels). Separated islands such as Madagascar contain many endemic species which have evolved in isolation. Isolated species may show convergent evolution: they evolve separate similar traits independently due to the adaption to similar ecological niches (these species are not closely related).
- 16how do fossils formMost fossils are the remains of hard parts of organisms, buried in sediment, they are common in aquatic environments. Fossils form when animals/plants die and the soft parts rot away and then get covered in sediment and solidify over time. Ground water dissolves leaving a mould in which minerals are deposited forming a cast. These fossils are then revealed millions of years later by erosion/movement of land
- 17how does the fossil record provide evidence for evolutionthe fossil record is a direct but fragmentary record of evolution. Some fossils can link the evolution of different groups e.g. Archaeopteryx-boned tail, teeth, feathers. Layers of known age allow is to place fossils in time (e.g. grand canyon). The fossil record shows a general trend of increased size, morphological complexity and diversity of animals.
- 18how does homology, vestigial structures and homoplasy provide evidence for evolutionhomologous characteristics (similar structures e.g. limbs, eyes etc) suggest that all organisms evolved from the same common ancestor.
Vestigial structures are poorly developed in some organisms, but fully developed in others e.g. hair, tails
Homoplastic characteristics are those which are similar in appearance and function but are fundamentally different and developed from separate evolutionary paths (e.g. wings). These have no common ancestry and evolved independently - 19how does embryology provide evidence for evolutionwhen vertebrate embryos are compared they all have common traits such as tails and gill slits. This indicates common ancestry
- 20how does comparative behaviour and biochemistry provide evidence for evolutioncomparative behaviour: social behaviour-the greater the similarity, the more closely related organisms may be e.g. chimps, apes
biochemistry-the molecular record
DNA contains a record of evolutionary change
mutation changes genes
evolution results from continuous changes in genetic composition
closely related organisms have fewer genetic differences. Less closely related organisms have more genetic differences
in the haemoglobin molecules of different species the amino acid chain differs. The amino acid sequence is closer in closely related species. The phylogenetic tree represents the evolutionary history of the globin gene - 21how does the hierarchal organisation of life provide evidence for evolutionour ability to divide the living world into a hierarchy of units suggests a history of branching and divergence
- 22what are the three domainsbacteria, eukaryotes, archaea
- 23what does the domain eukaryote consist ofeukaryotes (cells with nuclei within membranes). Kingdoms-protists, fungi, animalia, planae
- 24what are the six domains of lifearchaebacteria
eubacteria
protists
fungi
plantae
animalia - 25what are the main features of archaebacteriaprokaryotes that lack a peptide-glycan cell wall, e.g. extreme halophiles, thermophiles and methanogens
- 26what are the main features of eubacteriaprokaryotes with a peptidoglycan cell wall, e.g. cyanobacteria, soil bacteria, nitrogen-fixing bacteria and pathogenic bacteria
- 27what are the main features of protistseukaryotes, primarily unicellular organisms (some algae are multicellular). They are heterotrophic (gain nutrition by digesting organic matter, e.g. amoebas and paramecia) or photosynthetic organisms
- 28what are the main features of fungieukaryotic, mostly multicellular, (yeasts are single celled). They are heterotrophic, usually non-motile, with chitin cell walls e.g. mushrooms
- 29what are the main features of plantaeeukaryotic, multicellular, non-motile, usually terrestrial, photosynthetic organisms such as trees, grasses and mosses
- 30what are the main features of animalseukaryotic, multicellular, motile, heterotrophic organisms such as sponges, spiders, newts, penguins and humans
- 31describe the features of the early Earth part 1the Earth is about 4.5 billion years old. The early Earth was very hostile. The reducing atmosphere enabled the formation of carbon rich compounds. The temperature of the Earth was also high.
3.8 billion years ago life begins, the earliest fossils are of prokaryotes 3.5billion years ago, they had a simple structure-no nucleus and few internal structures. They were dominant between 3.5-2billion years ago. Examples of this life includes stomaltides-precambrian colonies of bacteria - 32describe the features of the early Earth part 2prokaryotes comprise of two main evolutionary branches, the bacteria and the archaea. The archaea include methane producers, thermophiles and halophiles. They are found in very hostile environments.
Cyanobacteria evolved 3.5billion years ago. They are oxygen-generating. These photosynthetic algae: raised atmospheric oxygen levels (over >billion years), enabling the ozone layer to form which protects the Earth from UV radiation - 33describe the features of the early Earth part 3eukaryotes evolved. A single-celled Eukaryote fossil has been found (800mya). Eukaryotes are larger and more complex than prokaryotes. They have a nucleus, chloroplasts and mitochondria. The eukaryotes are ancestral prokaryotes which underwent infoldings of the plasma membrane, engulfing of aerobic heterotrophic prokaryote, engulfing of photosynthetic prokaryote. This is an endosymbiotic relationship between bacteria
- 34describe the features of the early Earth part 4multicellular eukaryotes evolved from single-celled eukaryotes living in association with each other. Specialised cells develop, sexual reproduction was generally well developed, most eukaryotes are aerobic.
The fusion of gametes enabled genetic recombination. This was a huge step in the diversification of life because sex generates a lot more genetic variation than mutation, this enabled faster evolutionary change.
Jellyfish and worms evolved 600mya - 35describe the features of the early Earth part 5at the end of an ice age around 570mya there was an explosion in eukaryotic diversity. This was the early Cambrian period
The land was colonised by plants, animals and fungi about 500mya. The movement from aquatic to terrestrial life required numerous adaptions. This led to the transformation of the landscape by plants
most of the orders of modern mammals, including the primates, were established by 50-60mya. The human lineage diverged from primates about 5-6.5mya
organisms interact with their environment. The environment is altered by events which then effect evolution (i.e. the break up of continents, mass extinctions). The environment is also altered by the life that inhabits it (i.e. photosynthetic algae) - 36describe the relevance of mass extinction events to evolutionduring Earths history there have been several mass extinction events. Mass extinction events create ecological space by removing organisms that were occupying some niches. The survivors' descendants can evolve to fit those spaces with fewer constraints such as competition.
- 37what is adaptive radiationadaptive radiation may occur after mass extinctions or when new opportunities arise e.g. new islands. Adaptive radiation is the diversification of a group of organisms to fill different ecological niches
adaptive radiation of Darwin's finches:
ancestral finches arrive on island
there is a lack of small birds so there is no competition for food, space, etc
finches diverged to occupy different habitats
some evolved into different species. Finches with different beaks and feeding habits emerged - 38when was the primate super order established and what can this be split intothe primate superorder of Euarchonta was established 80mya and was split into the Prosimians and Simians. The primate evolutionary tree can be split into: Prosimians (lemurs, lorises, pottos and tarsiers) and Simians (or arthropoids) (new world monkeys, old world monkeys, gibbons, orang-utans, gorillas, chimpanzees and humans)
- 39what are some key features of Prosimiansgrasping fingers and toes, binocular vision, nocturnal, mostly arboreal (tree living)
- 40where did the Simians originatethe first simians (or higher primates) were direct ancestors of monkeys and hominoids which originated in Africa or Asia.
New world monkeys (e.g. marmosets, squirrel monkeys)-South America
Old world monkeys (e.g. macaques, baboons)-Africa and Asia
different adaptive radiations-40mya, land separated, NWM reached South America by rafting - 41what are the key developments of the first Simiansfirst Simians (higher primates). Key developments from Prosimians: overlapping fields of vision, opposable thumbs (not all genera), lived in groups, mostly diurnal
- 42describe which families the apes belong tooall apes are members of the superfamily Hominidea (the hominoids)
there are two families of hominoid: Hylobatidae (gibbons) the lesser apes and Hominidae: the great apes which consist of the orang-utans, gorillas, chimpanzees and humans - 43how similar are human and chimp genomesthere is a 96% overall similarity and a 99% similarity in coding DNA. This is a distance of 19 regulatory genes
- 44what are the key new characteristics of apeslarger brain relative to body size compared to other primates, flexible behaviour, tail-less, some highly social. The opposable thumb also developed (for grip)
- 45describe the human ancestry in terms of familiesHominoid--the apes superfamily
Hominid--the great apes family
Hominine--gorilla, chimp and human subfamily
Hominini--human and chimp tribe
Hominina--human subtribe - 46what does Hominina includeAustralopithecus and Homo
- 47what are the main features of Ardipithecus ramidusaround 4.4mya, chimp-sized brain, broader diet than modern chimps, partly bipedal
- 48what are the main features of Australopithecusa close H.sapien relation. All Australopithecus had: round jaw, brain size 35% of modern humans, stocky build, large teeth and jaws, various ways of moving but could walk upright
- 49when did the homo genus appear2.5mya
- 50what are the main features of H.habilis, H.erectus and Neanderthal manH.habilis-found with stone tools, short, disproportionally long arms, larger brain than Australopithecines. H.habilis was replaced by homo erectus
H.erectus-5 feet tall, used crude tools, built fires, social groups, cave dwellers/wooden shelters, Africa, ancestors of H.sapiens, long straight legs, excellent walkers, thick skull, larger brain, rounded jaw, ability to talk
Neanderthal man-600,000 years ago Europe and Asia, large skulls, bigger brains than humans, common 70,000 years ago, made tools of stone and wood, lived in huts and caves, took care of injured and sick, buried dead - 51what are the main features of anatomically or Early Modern Humanslooked like us but lacked certain modern behaviours, evolved 200,000 years ago and replaced Neanderthals by 30,000 years ago, sophisticated tools, complex social organisation, facial expressions, language, usually offspring/parental care, cave paintings, loss of body hair, pigmentation, lengthened thumb.
Successful hunters, colonised plains, spread across North America by 13,000 years ago - 52what two main models have been used to describe the origins of human evolutionthe multiregional model (model of parallel evolution)
(recent) out of Africa model (or replacement hypothesis, recent single origin hypothesis)
both models recognize that humanity originated from Africa - 53what are the main features of the multiregional hypothesisdebate focused on age of most recent hominid ancestor from fossil record
multiregional=last common ancestor in Africa 1.5mya
H.erectus scattered across Europe, Asia and Africa
similarities of modern people is a product of occasional interbreeding between neighbouring populations
H.sapiens evolved from each region of local populations of H.erectus 1.2mya - 54what are the main features of the out of Africa modelH.sapiens evolved to AMH (anatomically modern humans) in Africa 200-100ka and then colonised the rest of the world
they replaced regional descendants of H.erectus
if correct, global populations should be more closely related than if the multi-regional hypothesis was true
H.sapiens evolved from second major migration out of Africa 60,000YA - 55what is the evidence for the models of human evolution part 1mitochondrial DNA produced a tree with its origins in Africa, this dated the time of divergence at 200,000 years ago
a study comparing the Y chromosomes from various geographical regions found that Y has little crossing over during meiosis, i.e. diversity among Y's is limited to mutations. This can act as a marker for examining ancestry. Divergence from one male African ancestor was found to be 60,000YA - 56what is the evidence for the models of human evolution part 2Neanderthals split from descendants of African Homo migrants but then became extinct around 30,000YA
Neanderthals co-existed with AMH for at least 1000years
Mitochondrial DNA typing shows sharp differences between AMHs and available sequences for Neanderthals
this favours the out of Africa model, e.g. AMHs replaced Neanderthals - 57what is the assimilation model (a third option)important contributions were made by a recent ancestor from Africa
it emphasises assimilation rather than replacement as human ancestors colonised the rest of the world
this predicted that Neanderthals contributed about 10% of living peoples genome
recently a completed Neanderthal genome was sequenced, it shows 1-4% similarity with the DNA of Europeans and Asians, but not Africans. A new archaic species was discovered which was close to Neanderthals but not the same, and not a modern species. It was dated to about 30-50,000 years old. 4-6% of the girls DNA was the same as found in Melanesians; these segments are not found in Neanderthals or other modern humans - 58what are the main features of the leaky placement modelNeanderthals and Denisovan populations split about 200,000 years ago-they share some DNA
when modern humans left Africa, they interbred with Neanderthals approximately 100,000 years ago-these then evolved to modern day Asians and Europeans. A subset of the group went East and interbred with Denisovans-these form the basis of modern day Melanesians. Interbreeding is still limited.
Previous study assumes all populations were well mixed within continents, which is unlikely due to regional differences
this suggests that if Neanderthals and modern humans shared a common ancestor approximately 500,000 years ago then similarity could be due to a common ancestry rather than interbreeding - 59what does it mean to be humanbipedalism
permanent bisexual social groups
large brain: 1400c.c
capable of complex learning
advanced use of language
cultural development
food obtained through division of labour
similarities with primates include: reproductive strategies, enhanced communication/social behaviour, tool use - 60what are the two reproductive strategies and which is used by the primatesprimates produce few young, with high levels of parental care-k-selected
large numbers of offspring, little/no energy in parental care-r selected - 61what are the main ways in which apes use toolsorang-utans use sticks to get insects out of their nests
chimpanzees use rocks to smash open food and put leaves on their feet to walk over thorns - 62what are the possible scenarios for why human language developedsubstitute for grooming due to loss of hair
hunting theories
language as a way of thinking
motherese
tool making - 63what is theory 1 about why human language developedstarted with manual gestures
moved to vocal either because of a conflict with tool use or through association of gesture and sound - 64what is theory 2 about why human language developedmanual gestures were no use at night and require a direct line of sight
basic components of a speech derive from way we use our mouth to swallow/eat
or change in brain required for walking may have changed our brains in such a way to allow speech to evolve - 65how did agriculture develop in humansstart of halocene, cultivation of cereal grains started e.g. wheat and barley
domestication of livestock as food sources (9000YA)
commencement of global anthropological impacts - 66what are the drivers of human evolutionfluctuating environments lead to changing food sources and environmental conditions e.g. the expansion of the savannah/reduction of forest
e.g. Neanderthals developed short limbs and broad bodies to conserve heat in comparatively cold Europe
early hominids were vulnerable to predation. This lead to the use of fire as protection, stone tools as weapons, communication to warn others and the building of shelters-adaptability - 67what is the nature/nurture debate and how does it relate to human evolutionsociobiology-the evolutionary implications of behaviour
sociobiologists-compare our behaviour with other animals
predicts that heritable behaviours have evolved over time, similar to physical traits
genetic basis for complex human interactions remains controversial to some
only genetic information is passed on in simple organisms
higher animals (e.g. primates) also pass on environmental information from parents - 68describe the related theories of evolution (Lamarkism)heritability of acquired characteristics or instructions by the environment rather than selection by it (e.g. giraffes neck stretching)
there is little evidence that behaviour is not genetically determined
language and written disorders are more highly correlated in monozygotic twins than dizygotic twins
the FOXP2 gene is found in many species including humans and the removal/mutation of this gene is usually associated with impaired communications - 69what is microevolution in modern humanspolymorphisms: traits used to document genetic differences between populations
sickle-cell trait
ABO blood system
determined by genotype for ABO locus
geographical distribution of tawny hair in Australia - 70what is macroevolutionevolutionary change over long periods of time on a large scale. E.g:
origins of new taxanomic groups
evolutionary trends, e.g. convergence
new kinds of organisms penetrating new habitats e.g. adaptive radiation
mass extinctions - 71what is microevolutionit is the basis of natural selection, whereby a population progressively adapts to its environment
change at/below species level
a population is a group of individuals of the same species living in a particular geographical location
e.g. natural selection-individuals with heritable advantageous characteristics produce more successful offspring than those without the characteristic - 72define the terms genotype and phenotypegenotype-the genetic makeup of an individual
phenotype-observable characteristics (these depend upon an organisms genotype and on its environment) - 73define the terms chromosomes, homologous chromosomes, genes and alleleschromosomes-genes carrying structures found in the nucleus
homologous chromosomes-chromosomes that carry genes controlling the same characteristics. Most eukaryotes have pairs of homologous chromosomes; one set from each parent
genes are comprised of DNA
alleles are alternative forms of a gene-variation in the DNA sequence for a given gene - 74define the terms homozygous and heterozygoushomozygous-homologous chromosomes contain the same allele
heterozygous-homologous chromosomes contain certain different alleles
alleles can be dominant or recessive - 75what is asexual reproductionasexual reproduction is by mitosis: daughter cell are identical to parents-they are clones
asexual reproduction occurs by fission, budding, parthenogenesis, vegetative propagation and fragmentation
little genetic variation occurs - 76what is binary fission, budding, parthenogenesis, vegetative propagation and fragmentationbinary fission-one cell divides into two cells of similar size
budding-new individuals split from another
parthenogenesis-development of an unfertilised egg
vegetative propagation-new plants grow from runners of the parent plant
fragmentation-an organism splits into fragments which develop into mature, fully grown individuals that are clones of the original organism - 77what is sexual reproductionhaploid gametes formed by meiosis, fuse to form a diploid zygote. Offspring are genetically different from their parents. This is a result of:
1.) the independent assortment of chromosomes in meiosis
2.) exchange of DNA between homologous chromosomes by crossing over in meiosis
3.) random fertilisation-zygotes contain chromosomes from two parents
different alleles from each parent
in humans, each gamete represents 1 of 8 million possible combinations of chromosomes
each zygote has 1 of 70 trillion possible diploid combinations+variation from crossing over - 78what are the advantages of asexual reproductionin a stable environment the best genotype is perpetuated
uses less energy - 79what are the advantages of sexual reproductionproduces a lot of variation-new combinations may work better than previous ones
in a changing environment variation may promote overall survival - 80how are different alleles generateddifferent alleles are generated from chromosomal mutations such as deletion, duplication, inversion and reciprocal translation
- 81define the terms polyploidy, autopolyploidy and allopolyploidypolyploidy-multiple chromosomes
autopolyploidy-the chromosomes divide but the nucleus does not. Chromosome number increases from a diploid to a tetraploid (4 copies per cell)
allopolyploidy-related species interbred, hybridise, then chromosome number doubles - 82what are the main features of polyploidyresults in reproductive isolation
mating with a parent would yield triploid offspring (nearly always sterile due to resulting abnormal meiosis)
may be able to reproduce asexually
less significant among animals as self fertilisation and vegetative propagation do not usually occur
70% of all flowering plants are thought to have originated as a result of polyploidy, have some key agricultural crops such as oats, cotton, potatoes and wheat - 83what are the main features of molecular variationthis can be determined by comparing the structures of DNA, RNA and key proteins
the amino acid sequence of homologous proteins can be compared within or between species, and the number of differences compared
comparison of DNA and RNA sequences can also be performed
there is substantial variation within species
in humans, homologous chromosomes differ by about 0.5% of bases in DNA-this is equivalent to 15million bases
most of the DNA is non-coding "silent DNA"-and while it is not subject to natural selection, it will be changed by mutation and genetic drift - 84describe sickle-cell anaemia as an example of molecular variationvariation form of haemoglobin (normal genotype-HnHn)
point mutation
sickle-celled red blood cells
can be fatal in homozygous (HsHs) individuals
heterozygotes (HnHs) can lead normal lives
incidence of heterozygotes for sickle cell gene is greatest where most severe forms of malaria are present
people with normal haemoglobin (HnHn) are susceptible to malaria-heterozygotes are much less so
sickle cell heterozygotes are better adapted in areas where malaria occurs
selection pressure of malaria maintains lethal SC allele in the gene pool of the population - 85evolution requires changes in allele _____________ (microevolution)frequency
- 86what evolutionary forces effect change in allele frequencymutation, gene flow, genetic drift, natural selection
- 87what are the main features of mutationchanges in genetic code
more important if occurs in cells that produce gametes
current organism is likely to be well adapted to its environment, therefore mutations are more likely to be detrimental than beneficial
they don't always have an effect
generally low rates (1/100,000 genes per generation) small effects on large populations - 88what are the main features of gene flowall the alleles in a population are known as the gene pool
gene flow is the movement of genes between populations i.e. genetic exchange due to the migration of fertile individuals or gametes between populations - 89what are the main features of genetic driftchance alterations in a population's allele frequencies
genetic drift can be caused by:
A.) bottlenecks-a population bottleneck is an event that drastically reduces the size of a population
B.) Founder effects:
colonisation of a new area e.g. the Galapagos islands
one/few individuals of a species become founders of a new isolated population
rarer alleles in old population, may become significant in new population - 90what may cause a differential success in reproduction, i.e. some variants leaving more offspringclimate
avoidance of predators
resistance to pesticides - 91name the different modes of selectionstabilizing selection-both extremes are at a selective disadvantage
directional selection-one extreme is at a select disadvantage
diversifying selection-average individuals are at a selective disadvantage
all modes of selection lead to non-random changes in allele frequency - 92what are the main features of population growthinitial rapid growth-low density population
growth rate slows-maximum population size is eventually reached. This is the carrying capacity-high density population
different selection pressures act in each case
at high density populations, traits (adaptions) are favoured that enable reproduction with fewer resources
k selection-density dependent
at low density populations, selection favours traits that promote rapid reproduction
r selection-density independent u - 93what is speciationthe origination of a new species is driven by population divergence
a population is a group of individuals of the same species living in a particular geographical location
two modes of speciation are allopatric and sympatric - 94what is the difference between allopatric and sympatric speciationallopatric speciation-populations of a species are separated by a geographical barrier which leads to the formation of a new species
sympatric speciation-new species evolve from a single ancestral species while inhabiting the same geographical location
an example of sympatric speciation is autopolyploidy-the chromosomes divide, but the nucleus does not. Chromosome number increases from a diploid to a tetraploid (4 copies per cell) - 95what are the main features of reproductive barriersthese ensure new species keep their separate identities. Reproductive barriers can be either prezygotic or postzygotic
prezygotic-impedes mating between species or fertilization of ova if mating is attempted
postzygotic-prevents any ovum fertilized by another species from developing into a viable fertile adult
prezygotic barriers include habitat isolation, behavioural isolation, temporal isolation, mechanical isolation and gametic isolation - 96describe the different prezygotic reproductive barriershabitat isolation-2 species living in the same area but different habitats e.g. water and land snakes. These species rarely encounter each other and are technically not geographically isolated
behavioural isolation-an isolation mechanism in which two species do not mate because of differences in courtship behaviour
temporal isolation-a mechanism that prevents mating because species breed at different times (e.g. flowering at different times)
mechanical isolation- a form of reproductive isolation that occurs because of an incompatibility in structure of male and female sex organs
gametic isolation-gametes (egg and sperm) come into contact but no fertilization takes place - 97describe the different postzygotic reproductive barriersreduced hybrid fertility-when the first hybrid generations are fertile but their offspring are infertile e.g. mules
reduced hybrid viability-when hybrids have detrimental physical characteristics that make them more susceptible to change e.g. parasites, predators etc
hybrid breakdown
most species diverge as a result of combinations of certain pre and post zygotic barriers - 98what is gradualismgradual evolutionary change-slow but consistent rate of change
punctuated equilibrium-appearance of new characteristics give rise to new species relatively rapidly and then persist unchanged for a long time (equilibrium). New innovations result in a new spurt of evolution which would result in a punctuation of the fossil record - 99what is coevolutionspecies often interact, e.g. predators/prey, host/parasite, flower/pollinator
coevolution occurs when there is a selection pressure from another species and vice/versa. Selection may be positive or negative
coevolution occurs when selection pressures on one species are influenced by the evolution of another - 100what are the different types of co-evolutioninter-specific competition
exploitation-predation/parasitism
mutualism - 101what is inter-specific competitioninter-specific competition-competition between species may result in character displacement, this is when two species become more different when they occur together. E.g. Hydrobia ulvae and Hydrobia ventrosa-small estuarine molluscs, when in isolation (allopatric) each species is similar in size but when found together (sympatric) H.ulvae is always larger. This results in a diet different enough to avoid competition. The diet separation is greatest in sympatry
- 102describe exploitation using the example of the cuckoo part 1cuckoos are brood parasites which lay their eggs in the nests of other species
cuckoos arrive in Northern Europe in April and they set up a home range on a suitable habitat
reed warbler nests are a typical host for a cuckoo. Females lay single eggs in nests of other species, approximately 15 eggs per season
the cuckoo eats the egg, lays its egg and then flies off - 103describe exploitation using the example of the cuckoo part 2cuckoos sometimes destroy nests that have been incubated so the reed warbler makes a new nest which the cuckoo then lays in
the cuckoo chicks hatch before the eggs of the nests which they invade and once hatched they remove the competition
within three weeks the young cuckoo is ready to fledge-but wont fit into the nest
there is strong selection on the host to reject the cuckoo and a strong selection on the cuckoo to fool the host
there may be an evolutionary arms race-a series of adaptions and counter-adaptions e.g. cuckoo/host coevolution
host sometimes rejects cuckoo eggs
female cuckoos specialize on one species and lay eggs with consistent colour and patterns which tend to mimic host eggs - 104describe the Davies and Brooke model egg experimentsunsuitable hosts (hole nesters or seed eaters) do not discriminate. Icelandic meadow pipits do not discriminate (no cuckoos)
dunnocks may accept the egg because of an evolutionary time lag. They may be relatively new hosts as Dunnock relatives are mountain species (no cuckoos). An azure-winged magpie-a new host in Japan also shows poor mimicry and low rejection - 105what adaptions do cuckoos have to mimicrythe cuckoo has various adaptions such as egg mimicry, a relatively thick egg shell to prevent host removal and a small egg for body size. The cuckoo also lays its egg very fast, lays whilst the host is also laying and may re-start the host clutch. The cuckoo chick hatches fast for its size and removes the host egg/young
- 106why doesn't the host always remove the cuckoochicks grow very rapidly and are fast changing so identification of cuckoo may be prone to error. Parisitation rates are also less than 2%. Most stringent behaviour when identifying cuckoo chicks or eggs allows more chance for error, such as discrimination against the hosts own egg. This is a cost of discrimination as it could lead to the host rejecting its own offspring
- 107what is indirect coevolutioninsect oposematism is the term used to describe the use of bright colouration to advertise that the organism is dangerous or unpalatable. It is advantageous to stand out if the prey is distasteful
Gittleman and Harvey-predators learn to avoid some prey because of warning colouration which advertises prey as poisonous
Mimicry is an example of co-evolution from indirect selection. Wasps/bees and poisonous butterflies have non-poisonous mimics (e.g. hoverflies) which are avoided by predators. Mimics benefit from random mutation and selection, leading to the mimicry (this is not active copying). - 108what is mutualismco-evolution through mutually positive association e.g. pollination using flowers which adapted to attract insect pollinators as the flowers advertise nectar. Mutualism is where both parties benefit from co-evolution
- 109what is the red queen effectred queen to Alice "it takes all the running you can do to keep in the same place"
evolution is generally a constant dynamic state because species interactions are many and varied. Evolved changes in one species might effect many others and vice-versa, so evolutionary change is constant as coevolution occurs. The alternative would be extinction as your parasites became more prevalent, your predators became better hunters or your competitors faster eaters - 110what are the costs of reproduction part 1energetics-burning up calories, using up proteins and fats, etc
loss of future reproductive opportunity-risks taken or energy expended on current reproductive effort which reduces the opportunity to invest in future breeding attempts. E.g. predation risk, use up resources and risk reducing survival, etc - 111what are the costs of reproduction part 2there are two costs, mating effort and parental effort. Mating effort includes territory defence, mate attraction and female defence. It also includes flower production, nuptial gifts and mate guarding effort. Parental effort includes investment in gametes, foetus and parental care. The allocation of costs is a trade-off of mating effort vs parental effort. The balance can vary greatly between species and within sexes of the same species e.g. peacock. There is another potential trade-off of a number of young vs effort of care. Investment in gametes-there tend to be few large offspring or many small ones
- 112what are the costs of reproduction part 3it is important to know what the cost currency is-e.g. reduced survival, reduced fecundity (reproductive rate) etc. E.g. collared flycatchers which are made to work harder with manipulated clutch sizes survive ok but have smaller clutches the following year
- 113what are the main features of the number of offspring per breeding eventthe number of offspring per breeding event is extremely variable between species-parental care seems to explain this variation. This is also variable within species-e.g. some great tits have 6 eggs and others have 12
a.) environmental effects on costs of reproduction-costs may not always be obvious until conditions are extreme-e.g. high rainfall reduces survival of red deer hinds which raise a calf
b.) individual differences-individuals have different amounts of resources and optimise clutch size accordingly
c.) not all species show such variation-e.g. pigeons always lay two eggs - 114how is mating effort/parental effort often different for males and femalesmales sometimes provide no parental care-peacocks, red deer, lions
females sometimes provide no parental care-seahorses, jacanas, sticklebacks
so costs of reproduction are usually different for males and females - 115what is parental investment and what are some examples of thisparental investment is when resources are allocated from parent to offspring which increase offspring viability at a cost to the parent
some frogs and scorpions carry young on their back
some fish carry young in their mouths or pouches
weaverbirds build elaborate hanging nests to avoid snakes
emperor penguins undergo long incubation without food
birds and other animals provide food
elephants have 24 months of pregnancy and 12 months of suckling
chimps and humans provide extended periods of learning - 116give some examples of the costs of parental carethe costs of parental care are direct costs such as energy and resources, and lost reproductive opportunities. Penguins cannot feed while incubating, leading to weight loss. They lose 30-40% extra body heat to warm the egg. Other resources may, or may not be limiting. Wrynecks lay one egg per day and they stop laying when they feel a full clutch, removing the eggs can induce them to lay up to 76 eggs, so materials are not limiting.
In willow tits survival after breeding negatively correlates with offspring production. In song sparrows survival after breeding positively correlates with offspring production. In collared flycatchers the survival rates aren't altered by broad size manipulation, however offspring production negatively correlates with clutch size the following year
individuals within the population differ in the resources available to them e.g. territory quality varies, individuals are different ages, sizes, weights etc - 117what is the difference between natural selection and sexual selectionnatural selection causes the evolution of traits (morphological or behavioural) which enhance an organisms chances of survival
sexual selection causes the evolution of traits which give the owner a mating advantage over other individuals of the same species - 118discuss the main features of sexual selectionsexual selection led to the evolution of traits that reduce survival such as brightness and loudness, and the evolution of other traits which seem to have little survival value such as Bower birds obsession with blue and dragonflies barbed penis
- 119what are secondary sexual characteristicstraits which give organisms a mating advantage over others of the same sex are called secondary sexual characteristics. These traits differ between sexes. They aren't connected with gamete production or transfer e.g. weapons-antlers, horns, etc, sexual dimorphism and elaborate displays and colours
- 120why is it usually the males which compete for reproductive opportunitiesthis is due to gamete size and the potential rate of reproduction
Gamete size-males: sperm, very small, large numbers, cheap
females: eggs, large, small numbers, expensive
female investment per gamete is relatively high
potential rate of reproduction-males have a higher potential rate of reproduction than females e.g. humans
Male: mate (minutes), replenish sperm (day), find new mate....could breed 300x faster than female
Female: Mate (minutes), gestate (9 months), can breed again in 10 months - 121what is the operational sex ratiostart with 100 males: 100 females: pregnancy lasts 5 months
make 10 females pregnant-males ready to remate
operational sex ratio is now 90 available females:100 males
females are in short supply, so males compete for them
males are in excess, so females can afford to be choosy
the sex with the greater potential rate of reproduction (males) competes whilst the other sex (females) is choosy - 122what are the advantages of being choosyinvestment in eggs is relatively high and breeding opportunities are relatively rare
needs to get the right species and the best quality male available - 123sexual selection is separated into which two formsintra-sexual selection-competition against own sex for members of opposite sex, e.g. male fights, weapons-horns, antlers, signals-roars, croaks, songs. Size dimorphism-larger males win
inter-sexual selection-mate choice, individuals are variable, get right species, better resources (territory, food, nest sites, etc), better parental care, less harassment, offspring of better genetic variability or other quality - 124describe the evolution of antlersthe evolution of antlers and horns in ungulates such as Sable antelope, big horn Ram, Red Deer, Moose and Thompson's Gazelle is due to sexual selection and not natural selection. This is because often only the male has them e.g. Red Deer. Also antlers aren't always used for defence; moose defend themselves by kicking and not by using their antlers. They may be used for defence, but differ in shape e.g. female antelopes are thinner, but often less broken. Many ungulates also shed their antlers in the winter when predation risk is highest. Therefore their weapons evolved due to sexual selection.
- 125what are the main features of intra-sexual selection-sizemale competitions are often won by the largest male which selects for large size in males. This can lead to some extreme examples of size dimorphism e.g. male elephant seals weigh 10x that of the females
- 126what are the main features of intra-sexual selection-rituals and displaysfighting can often be dangerous, particularly in males with weapons, because neither male benefits from fighting, sizing up rituals are beneficial. Red deer-display increases in intensity 1.) roaring. 2.) parallel walking. 3.) fighting.
rituals can lead to some extravagant body parts e.g. stalk-eyed flies, peacock tails etc - 127why is there inter-sexual selection1.) to get the right species
2.) direct benefits-males may come with resources
3.)indirect benefits-males provide genetic benefits - 128what are the main features of getting the right specieshybrids are often infertile or less fit e.g. Australian Litoria frog-Litoria ewingi and Litoria verrauxi. There is a hybrid zone where these species overlap. Females have been under selection pressure to choose the right species to mate with. When placed in a choice chamber, females from the hybrid zone will always choose the correct male. Females from other areas make mistakes. Female preference is greatest when the cost of error is greatest e.g. will lead to failure to produce fertile offspring
- 129what are the main features of direct benefitsmales may come with direct resources such as food, nests, laying sites or territories, parental care and protection from harassment (e.g. from other males)
- 130what are the main features of indirect benefitsthe males genetic quality is passed to the offspring, this genetic quality includes parasite resistance, longevity (long life), sexiness etc. Mating with a high quality male therefore will lead to higher quality offspring and this will increase offspring viability
- 131read the rest of the stuff from the notebook because its way too big to be put on flashcards
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- Karteikarten am LEC 141: Evolution , erstellt von Oliver Dodd am 10/05/2017.
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- Oliver Dodd · Mai 2017
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