A4.1 Evolution and Speciation Flashcards
Evolution
cumulative change in the heritable characteristics of a population
development of life
what have scientists now understood about evolution
can happen rapidly not just geologically
theory of jean baptise Lamarck
physical changes occurring in a lifetime of an individual can be inherited by offspring
a blacksmiths children will inherit his muscles that he gets from working
changes through use and disuse
organs that are not used aren’t passed down and the ones that are used get adapted more and more each generation
inheritance of acquired characters lamarkism
an individual squires certain characteristics through their life which are then passed down to their children
effect of environment and new needs
change in the environment brings about changes and gives rise to new needs
produces new structures and changes the habits of organisms
example of acquire characteristic Lamarckism
giraffes neck
the giraffe wanted to reach leaves of trees to find new food so it stretched is neck
this was passed down to the next generation till the neck became very long
Darwins theory of evolution
variation within a population leafs to selection pressures
they pass their adaptation to their children
what does DNA knowledge for evolution show
shows that Darwin was correct by natural selection
variation caused by random mutations in DNA leading to alterations in the genetic makeup of species
epigenetic
the study of heritable changes un gene activity that are not caused by changes in DNA base sequences
what does epigenetics show
shows how environment factors that affect surviving of parents can alter the environment in which genes operate. changes can be inherited
why is epigenetic evolution not stable for evolutionary change
only lasts for a few generations
where does evidence for evolution come from
comes from many sources - study of fossils, artificial selection of domesticated breeds etc
what is the evidence from base sequences in DNA, RNA and AA sequences
biochemical commonality suggests a common origin of life because there are no such differences in the major processes of life such as respiration
large molecules are susceptible to change like DNA and protiens so its possible to measure relatedness of different groups of organisms bu the amount of difference between specific molecules
artificial selection
selection in breeding, carried out deliberately by humans to alter populations
what actually happens in artificial selection
involves identifying the largest, best or most useful of the progeny - use them as next generation parents
what is the outcome of artificial selection
continuous removal of progeny with less desired features leads to deliberate genetic change and genetic constitution of population to change fast
example of artificial selection
cereal crops
wheat, barely, oats and rice - most rice and have adapted to temperate climates with moderate rains
have been modified to produce more for the growing population
hard wheat
higher in protiens
grown in areas of lower rain
used to produce bread that can be kept for long
soft wheat
starchier
used for making pasta and French bread
grown in humid conditions
homologous structures
similar structures due to common ancestry
natural classification
organisms grouped by as many common features as possible, and therefore likely to reflect evolutionary relationship
example of evidence from homologous structures
limbs of vertebrates conform but show modification
they occupy similar positions in an organism, have a common underlying basic stricter but many have evolved different functions
phylogenetic classification
a classification based on evolutionary relationships rather than appearances
analogous structure
a feature in organisms
similar - function and superficial structure
different - fundamental structure and evolutionary origin
artificial classification
classifying organisms on the basis of few, self evident features
analogus features
- similar function
- different fundamental structure
- only superficial resemblances
- eg. wings of insects and birds
homologous features
- similar in fundamental structure, origin and position
- can be different in function
- eg. limbs of vertebrates
convergent evolution
the process by which distantly related organisms independently evolve analogous traits due to similar selection pressures
divergent evolution
occurs when an ancestral species spits into two reproductively isolated groups causing each group to develop different traits due to their respective selective pressures and natural selection
speciation
the process by which new species from, where one species is split into two or more species
speciation by splitting of existing species
when they are separated different environmental factors would act on them causing selection process again
why is progressive evolutionary change not speciation
inbreeding keeps the same gene pool
how does barrier lead to evolution
separating population means they cant inbreed
overtime through natural selection adaptive genes are chosen
2 gene pools change and evolve
roles of reproductive isolation and differential selection in speciation
before separation, individuals share a common gene pool, but after isolation - disturbing processes such as natural selection, mutation and random genetic differences.
reproductive isolation
different species cant interbreed to produce fertile offspring
when members of related populations have evolved to this point and have become fully reproductively isolated they can have fertile offspring with members of different species
geographical isolation
when barriers arise and restrict the movement of individuals between divided populations
barriers can natural or man made
