evolution Flashcards
what is a scientific theory?
a mature, coherent body of interconnected statements based on reasoning and evidence
explains some aspects of nature
what is evolution not?
not the same as natural selection
not something from the past but continuously occurring
doesn’t happen to individuals but populations
what is evolution?
the change in properties of groups of organisms over the course of generations
ie descent with modification
history of evolution thinking
previous thought was essentialism
relates to how everything is present of a continuum from inanimate to supernatural
led to ideas about how organisms are structured naturally
James Hutton
made geology a science
wrote ‘Theory of the Earth’
Charles Lyell
principles of geology
study of rock layers
influential to Darwin
Jean-Baptiste de Lamarck
life had originated many times
overtime, lineages become more complex
all complexities exist at one time
- simple forms and older more complex forms
what did Darwin and Wallace publish?
theory of evolution by natural selection
copublished
similarities between Darwin and Wallace
evolution as a fact
common descent
changes are gradual
populations changing not individuals
caused by natural selection
differences between Darwin and Wallace
Darwin emphasised competition between individuals of the same species to survive and reproduce
Wallace emphases environmental pressures on varieties and species forcing them to become adapted to their local environment
acceptance of the theory
general acceptance of evolution
but rejection of natural selection
- no mechanism of inheritance ti explain traits being passed on
- blending theory of inheritance is not compatible with natural selection
Neo-Lamarckism
acquired traits can be passed on
orthogenesis
‘straight line’ evolution towards a fixed goal
mutationist
major mutations gave rise to new phenotypes
some of which constituted a new species
the modern synthesis
marriage og genetics and natural selection
mutation as raw materials for selection rather than alternative
development of mathematical theory
theory and empirical population genetics
applying concepts across fields
developments since the modern synthesis
extension of evolutionary theory
- ecology, behaviour
molecular evolution
evolutionary development
macroevolution
bias in the theory
scientist occurs in all societies not just western world
eg lack of representation of muslim scholars
lack of women
eugenics
new understanding of evolution by natural selection opted as means of improving human society
- science of improving human stock
examples of eugenics
Churchill campaigned for sterilisation of undesirables
pedigrees traced to establish inheritance of desirable and undesirable traits to purify American people
nazi laws to sterilise people such as schizophrenics and the blind
eugenics in modern society
discussions of overpopulation and eco-facism
evolutionary racism as the motivation for mass shooting
white replacement theory - black outbreeding white people
what is a mutation?
any change in the nucleotide sequence of DNA
can be deleterious (harmful) or neutral (no effect)
origin of genetic variation
causes of mutation
DNA damage by mutagens
errors in DNA replication
synonymous vs nonsynonymous mutations
synonymous - the amino acid sequence does not change
non synonymous - amino acid sequence changes
results of mutations
loss of function
gain of function (rare)
mutation rates among regions of the genome
base composition
- transitions and transversions occur at different rates
position in the genome
- centromeres vs chromosome tips have different rates
presence of epigenetic modification
mutations rates among organisms
depends on
efficiency of their DNA repair mechanisms
exposure to mutagens
relationship between genome size and mutation rate
viruses and prokaryotes:
smaller genome so higher mutation rates
multicellular organisms:
larger genomes so higher mutation rates
gene pool
sum of all copies of all alleles within a population
selection
occurs when there is a difference in the survival and/or reproduction of individuals based on their phenotypes
survival and reproduction summarised as fitness
increases the frequency of the favoured trait in next generation
natural selection
when the difference in fitness occurs due to conditions in biotic or abiotic environment
eg peppered moth
artificial selection
when the difference in fitness occurs due to human preference for traits
eg selective breeding
critically important process in human history
- basis of crop and livestock improvement
- development of breeds
sexual selection
when individuals mate preferentially with particular individuals rather than at random
influence fitness
has power to favour traits and enhance chances of reproduction, even if reduce chance of survival
impact of sexual selection on fitness
important as individuals that survive but don’t reproduce make no contribution to next generation
= no fitness
how do mating patterns impact an individuals fitness?
survival due to natural selection
reproduction relies on sexual selection
limited by need for a balance between survival and reproduction
eg peacock tails
adaptation
characteristic that enhances the survival or reproduction of organisms
process by which members of a population become better adapted to their environment
migration
movement of individuals or gametes
if migrants survive and reproduce then gene flow occurs
gene flow
caused by migration
changes allele frequencies in a population in proportion to the rate and direction of migration
genetic drift
random chances in allele frequencies from one generation to the next
driven by chance not selection
impacted by meiosis and random survival
larger impacts in smaller populations
- in larger, many more generations required before allele eliminated or fixed
mechanisms in an unstable population
population bottleneck
founder effect
population bottleneck
when a population is dramatically reduced in size
by chance the small number of survivors may not be representative of the original population
reduces genetic variation
eg elephant seal
founder effect
when a population is started by a small number of individuals
they are unlikely to possess all of the alleles found in the gene pool of the source population
founder population less variable than original
rare alleles are likely lost
reduced genetic variation
processes in evolution
mutation
selection (natural and sexual)
gene flow
genetic drift
non random mating (sexual selection)
all occur at the same time in a natural population
