evolution
Darwinian evolution
Charles Darwin
he was born in Shrewsbury western England, he was forced to go to medical school but he quit, and became a clergyman
he went on a voyage called the HMS Beagle
he had describe that organisms had features that made them suited for their environment
ex: the Galapagos finches, different sized beaks because of their type of food they had
Darwin observed adaptions in animals as it enhanced their survival and reproduction
natural selection certain inherited traits in organisms survive and reproduce more successfully than other individuals
descent with modification can help explain natural selection
Darwin had evidence on 3 observations about nature
unity of life, diversity of life, match between organisms and their environments resulted from descent with modification by natural selection
unity of life, organism had an ancestor
descendants of ancestral organism lived in various habitats, and adapted
observable patterns of evolution
selective breeding called artificial breeding
selecting & breeding based on desired traits
ex: dog breeders
Darwin's observations and inferences
observation 1,members of a population vary in inherited traits
- natural selection occurs between animal and environment, but individuals don't evolve rather its the population
- NS can diminish or amplify heritable traits that differ among individuals in a populations
- environmental factor change place to place & over time
traits are favored depends on which the species lives and mates
traits can useless or detrimental depending on the environment
2, offspring are overproduced in an environment, fail to survive & reproduce
inference 1, inherited traits that give a higher chance at surviving & reproducing leave more offspring than those who dont
2, unequal ability to survive, causing favorable traits to accumulate
evidence for evolution
ex: soapberry bugs beaks length based on food source and where they live
they have a needlelike mouth part, one feeds on native balloon vines in southern Florida, the other feeds on golden rain tree in central Florida
homology, related species have characteristics hat have an underlying similarity but function differently
ancestral organisms had characteristic that are altered in the descents over time when faced different conditions
def; related species have underlying similarity but function differently
ex: forelimbs in humans ,cats, whales, bats
resemblance of arrangement but have different functions. assuming that there had been a structural theme in a common ancestor (homologous structures)
left over structures, vestigial structures remnants of features that served a function in an organism ancestor
(ex: snakes retain pelvic bones and leg bones of ancestors)
distantly related organism resemble each other b/c of convergent evolution
the independent evolution of similar features in different lineages
ex; sugar gliders and flying squirrels
analogous, features share similar function but not common ancestry
homologous, common ancestry, but not same function
fossil record
can document patterns of evolution, on how past organism differed from todays organisms
ex: pelvic bone in in fossil stickleback fish reduced in size over time in a # of different lakes
they also show evolutionary changes occurring in various groups
biogeography
geographic distributions of species that is influenced by factors ex: continental drift
evolution of populations
genetic variation, differences among individuals b/c of their genes and DNA sequences
some heritable phenotypic differences occur on an either or basis ex: flower color ( Mendlas pea plants)
characters that vary this way they are determined by a single gene locus
or some phenotypic differences vary in gradation along a continuum, results from the influence of two or more genes on a single phenotypic character
some phenotypic variation don't result from genetic differences in individual ex: muscles
Hardy Weinberg equilibrium
a population is not evolving, so allele and the genotype remain constant from generation to generation
3 ways allele frequencies are altered that cause evolutionary change
1)natural selection, alleles being passed to the next generation different from the present organism ( fruit fly restistant to insect ides)
favoring alleles over other ones NS causes adaptive evolution (better match between organisms and environment)
2)genetic drift, chance events causing allele frequencies to change unpredictably (in small populations)
ex: founder effect, organisms isolated from a large population, establish a new population differing the genes from the source (members are blown by a storm to a new island)
this causes genetic drift to happen
founder effect higher possibility of inherited disorders
ex: bottleneck effect, sudden change in the environment reduces population size. fire,flood
alleles become either overrepresented in survivors, or underrepresented, or some completely absent
genetic drift affects the gene pool until the population can get large again so chance events have less impact
3)gene flow, transfer of alleles in and out of a population b/c of fertile individuals and their gametes moving
b/c alleles are transferred, gene flow reduces genetic differences between populations
gene flow can combine two populations into one having a common gene pool
alleles transferred affect the population and how they are adapted to their environment
gene flow also transfer alleles that improve the ability of the population to adapt to the local conditions (insecticide-resistant alleles)
gene flow is important for evolutionary change in humans (we move freely, so exchanging of alleles and having less genetic drift between population)
what are species
speciation, one species splits into two or more species ex: it helps explain features that organisms share
comparing morphology of organisms, but also their physiology, biochemistry and DNA sequence. we understand that animals differ not just in morphology
the biological species concept is a way to describe species.
Species a group of population which they have the potential to interbreed in nature producing viable fertile offspring
the concept also states that species can't reproduce with other groups ex: humans & chimpanzees
species concepts
biological concept, species a group of a population interbreeding in nature producing viable offspring, but not with other members of other groups
members in this concept reproduce b/c of their compatibility
b/c of their compatibility, reproductive isolation
morphological concept, differ organisms based on body shape & other structural features
ecological concept, species defined b/c of its ecological niche meaning how species interact with living & nonliving things in the environment
phylogenetic concept, small group of individuals sharing a common ancestor forming a branch on the tree of life
determined by comparing morphology, molecular sequences with other organisms
the concept distinguishes organisms that are different and considered them to be separated species
it also applies to sexual and asexual organisms
this concept is basically subjective criteria making that a disadvantage
it also applies to sexual and asexual organisms
a disadvantage is that it can tell how much of a difference there is for the species to be considered separated
speciation with or without geographic separation
allopatric speciation, population are geographically isolated limiting gene flow ex: change in location resulting in a separated population
it can also occur with having geographic isolation, b/c some organisms can colonize remote areas and that could be a way they get geographically isolated
geographic separation causes divergence in gene pools, mutation arise, natural selection, genetic drift can change allele frequencies
ex:mosquito fish pg.505
sympatric speciation, occurs in populations living in the same geographic area
it also occurs when gene flow is reduced, by polyploidy, sexual selection, & habitat differentiation
1) polyploidy, an organism get an extra set of chromosomes b/c during cell division there was an accident
2) autopolyploid, organisms has more than two chromosome sets from a single parent
3) allopolyploid, is when sterile hybrids change into a fertile polyploid. b/c allopolyploid are fertile when they mate together but cant interbreed with parent species
this also occurs when two species interbreed resulting in a hybrid
sexual selection, occurred in cichlid. the females choose the males based on appearance in this case color
pundamilia pudamilia are blue-tinged, and the pundamilia nyererei are red-tinged back
homologous structure, variations that are structural theme present in a common ancestor
b/c females only mated with the color in their habitat causing reproductive barrier keeping the gene pool of the species separate
habitat differentiation, is another way that sympatric speciation occurs. exploitation a habitat or resource that is not used by the parent population
ex:the apple maggot fly, original habitat was hawthorn tree but some colonized apple trees. they feed on or near the host plant
b/c the flies use this it results in prezygotic barrier between the populations
new species can arise of mixed ancestry b/c it was produced by two different species mating and meeting called hybrids
the way that the parent population meet, an area located where interbreeding species meet is called the hybrid zone,
hybrids are produced b/c there is no reproductive barrier stopping the two species from meeting
hybrid zones over time in 3 ways
prezygotic barriers should be stronger so that hybrids formation is reduced which is called reinforcement
two species are able to come in contact, the reproductive barriers have weaken b/c of too much gene flow and they become alike this is called fusion (ex: lake Victoria cichlids fish)
stability, the zone continues to produce hybrids. this takes place b/c hybrids survive & reproduce better than the parent population in certain habitat and years
the alleles and genotype are always changing in real population, this happens b/c the equilibrium are not met
1) no mutations, 2) random mating, 3) no natural selection, 4) extremely large population size, 5) no gene flow
sources of genetic variation
which evolution depends originates when mutation, gene duplication, or process produce new alleles and genes
new alleles can arise by mutations, meaning a change in the DNA nucleotide
a change in one base pair can result in a point mutation which can have an impact on phenotype
mutations that alter phenotype are least slightly harmful, so natural selection removes those alleles
diploid organisms with harmful recessive alleles, these alleles can be hidden from natural selection
but there are some mutation aren't always harmful. the point mutations in these non-coding regions result in neutral variation
neutral variation, there is no advantage or disadvantage if there are differences in DNA sequences
altering gene number or position
chromosome changes that delete, disrupt, or rearrange are harmful
translocation of one chromosome to a different one, linking genes that can have a positive effect.
so a source a variation is the duplication of the genes b/c their was an error in meiosis, or slippage during DNA replication, or activities of transposable elements
pangaea, 250 million yrs ago this movement united all of the earths continents into a large continent
endemic, a species that is found nowhere else in the world. plants and animals