Evolution

Question 1

By 19thcentury

Answer 1

*Accepted that earth in the range of millions of years
*Acceptance of fossil record
*Similarities among different spp noted
*Descended from previously existing organisms
What natural mechanism could explain why organisms change?What herditary mechanism could enable organisms to change?

Question 1

Principle of Evolution

Answer 1

*Natural Selection leads to adaptation.
*Evolution (change) driven by changing environment.(Populations may change very little when conditions are constant).
*Natural selection NOT necessarily life or death: improved fitness may simply improve reproductive success.
Accumulation of changes may lead to speciation (i.e. development of new species).Extinction is common.
*Evolution never yields a predictable outcome, although natural selection and past evolutionary history may“steer” the evolution of a species in a particular direction. Mutations arise by chance and are then acted upon by natural selection

Question 2

Fossil Record

Answer 2

Fossil record is set in a framework of geological time.
Rocks are “dated” by Radiometric dating i.e.Half-life decay of radioactive elements

Question 3

Dating rocks

Answer 3

Radioactive elements decay into other elements at a fixed rate resulting in a 50% loss of the original element over a fixed period of time. If the first 50% is lost in 5600 years. We refer to this as the “half-life” of the element

Question 4

Testing the Hypothesis of Evolution

Answer 4

To test whether the phenomenon of evolution is supported or falsified by evidence:
1. The age of the earth should be “old”.
2. Fossil Evidence: change in composition; simple to complex; increasing diversity.
3. Morphology, physiology, biochemistry and genetics should all reflect an evolutionary tree: closely related spp share most characteristics.
4. Existence of intermediate forms.
5. Populations of species should change (adapt) as conditions change.
6. Change from one species to another.
7. Biogeographical distribution should reflect evol. history

Question 5

Source of information about biodiversity

Answer 5

1. Living forms
2. Fossil Record

Question 6

Fossil Evidence

Answer 6

“Fossil” refers to the preserved traces or remains of ancient organisms
“fossil” is derived from Latin word ‘Fossilis’ = ‘dug up

Question 7

Fossil record provides vital info about

Answer 7

ORIGINATION
DIVERSIFICATION
EXTINCTION

Question 8

Oldest traces of life

Answer 8

Barberton Greenstone Belt, South Africa 3.5my
2. 1 Billion-year-old multicellular life forms discovered in Gabon

Question 9

Criteria for Homologies

Answer 9

Same basic structure; same relationship to other features; same development. Shared derived characteristic.

Question 10

Analogous Structures

Answer 10

They have separate Evolutionary origins but are superficially similar because they evolved to serve the same function. Evidence for convergent evolution.

Question 11

Genetic similarity

Answer 11

genetic code is similar across the entire range of living organisms- suggesting common ancestry. Closely related species share greater proportion, than distantly related spe

Question 12

Globin

Answer 12

common in bacteria, plants, animals, and fungi; it binds and carries oxygen; through duplication and divergence different copies of globin molecules adapted for different roles.

Question 13

Ontogeny recapitulates phylogeny

Answer 13

Species that share a common ancestry should have similar embryology

Question 14

Adaptation

Answer 14

An adaptation is a feature that is common in a pop. because it provides some improved function e.g.,a behaviour that allows better evasion of predators;a protein that functions better etc

Question 15

Natural selection

Answer 15

differential success in reproduction (the unequal ability of indiv to survive and reproduce). Organisms with traits better suited for the environment, produce more offspring

Question 16

What does fittest actually mean?

Answer 16

“Fitness” relates to characteristics that affect an organisms chances of reproducing and/or surviving

Question 17

Natural selection (NS) does not produce perfect trait

Answer 17

1. NS only acts on available variation
2. Constraints due to evolutionary history
3. Trade-offs –adaptations are often compromises NS can affect levels of variation by being stabilising, Diversifying and directed

Question 18

Isolation of Australi

Answer 18

convergent evolution between marsupials and placentals; marsupials and placentals evol to fill same ecological niches

Question 19

Summing up

Answer 19

1. None of the lines of evidence that can be used to testthe hypothesis of evolution has allowed rejection of the concept.
2. Evolution (descent with modification) is real
3. Darwin’s four central ideas about mechanism of evol.are strongly supported by evidence
4. His views on the mechanism of evolution pre-date genetics so are insufficient to explain all aspects of evolution, especially with regard to (a) how new varieties arise and are inherited, and (b) the origin of new species

Question 20

Central ideas of Darwin’s theory of Evolution

Answer 20

1. More offspring are born than survive to reproduce
2. Variety exists in all species
3. Those varieties that are “better adapted” to the environment are more likely to survive and reproduce -“survival of the fittest”. Less “fit individuals are weeded out by Natural Selection.
4. If the characteristics of different varieties are inherited by their offspring, then the nature of a species will slowly change.

Question 21

Geographical isolation

Answer 21

One population is divided into two or more smaller pop because of mountains, rivers change course, or continents drift; Populations are prevented from interbreeding

Question 22

Reduction of gene flow

Answer 22

No specific extrinsic barrier. Consider spp that inhabit a broad geog range- individuals in the far west don’t mate with individuals in the far east- get zero gene flow, but not total isolation- which could lead to speciation

Question 23

Modes of speciation

Answer 23

Allopatric (allo- other)Geographically isolated pop
Peripatric (peri – near)Small pop isolated at edge of Larger pop
Sympatric (Sym- same)within range of ancestral pop
Parapatric (para- beside)A continuously distributed population

Question 24

Sympatric

Answer 24

Sympatric speciation often involves chromosomal changes and non-random mating that reduces gene flow. For example, if a group within a population starts to exploit a new ecological niche or food source, they may develop different behaviors or traits that lead to reproductive isolation from the rest of the population.

Question 25

Parapatric

Answer 25

For example, if a group within a population starts to exploit a new ecological niche or food source, they may develop different behaviors or traits that lead to reproductive isolation from the rest of the population.

Question 26

Sexual reproduction

Answer 26

Sex. Reprod. results in genetic shuffling -introd. new gene combinations in a pop. and results in genetic variation. When eggs and sperm are prod. parent cell copies each chromosome. Leaving duplicates attachedMatched pairs exchange DNA. The embryo will have genes from 4 grandparents.

Question 27

Genetic Drift (GD

Answer 27

In each generation, some indiv. may just by chance have more offspring than others. The genes of these indiv. will have a higher frequency (doesn’t mean that they Are healthier or better indiv.)
GD - Evolutionary equivalent to a sampling error Reduces genetic variation
2. More drastic in smaller populations (esp. rare and endangered species)

Question 28

Founder Effect

Answer 28

Few individuals become isolated from a larger population, small group may establish a new population whose gene pool differs from the source population

Question 29

Bottleneck Effect

Answer 29

Size of the population is greatly reduced by sudden events (e.g. fire, flood etc.,)
* The remaining population no longer represents the original. By chance - some alleles can be overrepresented, underrepresented, or even absent from the surviving population

Question 30

Sexual Selection (SS

Answer 30

Refers to natural selection that acts on mate-finding and reproductive behaviour. SS acts on an organism’s ability to obtain a mate and pass on one’s genes to the next generation

Question 31

MACROEVOLUTION

Answer 31

All the changes, diversification, and extinctions that occurred over the 3.8 by of history of life on earth are the patterns of macroevolution