Chapter 22 Whale Evolution Supoorted By Several Independent Lines Of Evidence Flashcards
Anatomy - how does it support whale evolution
Whales are mammals
- warm blooded
- hair, lungs, placenta, and produce milk
- bear live young
- 2 nasal passages (1/2blow holes)
- arm, wrist and finger bones and some VESTIGIAL pelvis/ legs
- tail moves vertically
A different cause of resemblance, other than homologous anatomy due to ancestors, is …..
CONVERGENT EVOLUTION
Is the evolution of similar or analogous features in distantly related groups
Analogous traits arise when groups independently adapt to similar environments in similar ways
Does not provide info about ancestry !!!
Had similar problems to environments and handled it in similar ways resulting in similar features E.G. BATS AND BIRDS
Wings didn’t come from ancestors it came from the fact that bats needed the ability to fly for environment over time = adaptation (natural selection)
Development and embryology- how does it support whale evolution
Vestigial strictures: hind limbs
Reminant of passed life style (ancestors) used to have. This slowly disappears however is still here
Embryology and homology
Comparative embryology reveals anatomical homologies not visible in adult organisms
Eg all vertebrate embryos have a post-anal tail and pharyngeal arches
Paleoecology/ sedimentology - how does it support whale evolution
Stable oxygen isotopes in modern and fossil cetaceans
Bars shifted to the left = ingested freshwater
Bar shifted to the right = ingested marine water
Modern marine and freshwater cetaceans
18- doesn’t evaporate quick because it’s heavier (marine animals)
16- evaporate quicker because it’s lighter (fresh water)
Pakicetus
Freshwater = 16
Ambulocetus
Transitional
Geogiacetus, Indian protocetids, remingtonocetus
Clearly marine
DNA and Genetics - how does it support whale evolution
If cetaceans really evolved from terrestrial mammals then it should also be reflected in their DNA
NUMEROUS MOLECULAR STUDIES HAVE CONFIRMED that hippos are the closest living relative to cetaceans (eg sister taxa)
Phenotype
Physical characteristics
Phenotype is the product of inherited genotype and environmental influences
Genotype
Genetic characteristic
Example of how natural selection acts on individuals but only populations evolve
A population of medium finches on daphne major island
During a draught large beaked birds were more likely to crack large seeds and survive
Finch population evolved by natural selection
Microevolution
Change in allele frequency overtime
3 mechanisms that cause allele frequencies to change
1) natural selection
2) genetic drift
3) gene flow
ONLY NATURAL SELECTION CAUSES ADAPTIVE EVOLUTION
Natural selection and Genetic variation
Natural selection can only act on variation with genetic component
Eg natural selection can’t influence phenotypic variation due to environmental forces
VARIATION IN HERITABLE TRAITS-
is a perquisite for evolution
How do new genes and alleles arise:
Mutations
Gene Duplication
Sexual reproduction
Mutation
Detrimental (harmful), neutral, beneficial
Can be hidden in recessive alleles
Gene duplication
Duplication of small pieces of DNA increases genome size!!!
Allows duplicate genes to take on new functions by further mutation
Ancestral door detecting gene has duplicated many times - human copies of the gene 350, mice have 1000
Sexual reproduction
Can result in genetic variation by recombining existing alleles
Organisms that can reproduce sexually, recombination of alleles is more important than mutation in producing the genetic differences that make adaptation possible.
Gene pools
Consists of all the alleles for all loci in a population
Locus
Is fixed if all individuals in a population are homozygous for the same allele
Population
Is localised group of individuals capable of interbreeding and producing fertile offspring
Fossils - how does it support whale evolution
Numerous fossils show a clear shift in habitat from terrestrial to aquatic and a radical change in form over millions of years.
