Chapter 22 Whale Evolution Supoorted By Several Independent Lines Of Evidence

Question 1

Anatomy - how does it support whale evolution

Answer 1

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

Question 2

A different cause of resemblance, other than homologous anatomy due to ancestors, is …..

Answer 2

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)

Question 3

Development and embryology- how does it support whale evolution

Answer 3

Vestigial strictures: hind limbs

Reminant of passed life style (ancestors) used to have. This slowly disappears however is still here

Question 4

Embryology and homology

Answer 4

Comparative embryology reveals anatomical homologies not visible in adult organisms

Eg all vertebrate embryos have a post-anal tail and pharyngeal arches

Question 5

Paleoecology/ sedimentology - how does it support whale evolution

Answer 5

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)

Question 6

Pakicetus

Answer 6

Freshwater = 16

Question 7

Ambulocetus

Answer 7

Transitional

Question 8

Geogiacetus, Indian protocetids, remingtonocetus

Answer 8

Clearly marine

Question 9

DNA and Genetics - how does it support whale evolution

Answer 9

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)

Question 10

Phenotype

Answer 10

Physical characteristics

Phenotype is the product of inherited genotype and environmental influences

Question 11

Genotype

Answer 11

Genetic characteristic

Question 12

Example of how natural selection acts on individuals but only populations evolve

Answer 12

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

Question 13

Microevolution

Answer 13

Change in allele frequency overtime

Question 14

3 mechanisms that cause allele frequencies to change

Answer 14

1) natural selection
2) genetic drift
3) gene flow

ONLY NATURAL SELECTION CAUSES ADAPTIVE EVOLUTION

Question 15

Natural selection and Genetic variation

Answer 15

Natural selection can only act on variation with genetic component

Eg natural selection can’t influence phenotypic variation due to environmental forces

Question 16

VARIATION IN HERITABLE TRAITS-

Answer 16

is a perquisite for evolution

Question 17

How do new genes and alleles arise:

Answer 17

Mutations

Gene Duplication

Sexual reproduction

Question 18

Mutation

Answer 18

Detrimental (harmful), neutral, beneficial

Can be hidden in recessive alleles

Question 19

Gene duplication

Answer 19

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

Question 20

Sexual reproduction

Answer 20

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.

Question 21

Gene pools

Answer 21

Consists of all the alleles for all loci in a population

Question 22

Locus

Answer 22

Is fixed if all individuals in a population are homozygous for the same allele

Question 23

Population

Answer 23

Is localised group of individuals capable of interbreeding and producing fertile offspring

Question 24

Fossils - how does it support whale evolution

Answer 24

Numerous fossils show a clear shift in habitat from terrestrial to aquatic and a radical change in form over millions of years.