Introduction to Evolution (Wellman)

Question 1

Basic Concepts of Neo-Darwinian Evolution

Answer 1

1. Reproduction: Same species reproduce to give viable offspring.
2. Excess: Too many offspring to survive needs to happen so bad characteristics can be removed.
3. Variation: Offspring are always different. Asexual reproduction; mutations, sexual reproduction; crossing over, blend of parents, Mendel’s law of segregation.
4. Environmental selection (natural selection): Environment varies, better adapted to that environment = more likely to reproduce = pass on genes. If not, genes become extinct.
5. Divergence: Certain genes passed on, others become extinct. Population diverges.
6. Ancestry: Life evolves once, we are able to trace ancestry back (tree of life).

Question 2

Biodiversity

Answer 2

‘Biodiversity is the variety of life, in all its manifestations. It encompasses all forms, levels and combinations of natural variation’

Question 3

Taxonomy

Answer 3

Taxonomy is the science of classification of organisms

Question 4

Phylogeny

Answer 4

Phylogeny is the study of evolutionary relationships

Question 5

Difference between taxonomy and phylogeny

Answer 5

Taxonomy is established on a time line, however phylogeny does take into account time

• Taxonomy = classification
• Phylogeny = evolutionary relationships

Question 6

Age of the Earth

Answer 6

Usher (4000bc) used genealogy in the bible to estimate that the earth was 6000 years old.

• After research into rocks it was found that it was impossible because some rocks couldn’t have formed in only 6000 years, i.e. the White Cliffs of Dover.
• It was also disproved by radioactive materials as radioactive decay could not have occurred in only 6000 years.

-After research, into rocks, radioactivity and salt water (how long until it becomes saline), and much, much more, it has been concluded that the earth is 4.6 billion years old.

Question 7

How can extant organisms be studied?

Answer 7

Sequence the DNA of a range of species and compare to see how related they are. Taxonomy can be compared to phylogeny.

Question 8

How can extinct organisms be studied?

Answer 8

Fossil Record. E.g. research into fossils showed that dinosaurs gave rise to birds.

Question 9

Marine animals in the fossil record

Answer 9

Marine animals are preserved because when they die they float down to anaerobic zone, where there is no bacteria to break it down. Learnt from fossil record that there are marine reptiles that from the Jurassic era

Question 10

Why is the fossil record incomplete?

Answer 10

1. Very few of the organisms that ever live will end up being fossilised (and ultimately collected and studied).
2. Entire species or higher taxa may not be preserved in the fossil record. This is particularly true for those:
   - With low preservation potential
   - With a small population
   - That inhabit a small geographical area
   - The lived for only a short period of time

Question 11

Why is the fossil record biased?

Answer 11

1. Certain environments are more likely to be preserved that others, i.e. those with new deposition rather than net erosion. Thus:
   - Marine organisms are more likely to be preserved than terrestrial organisms
   - Terrestrial lowland deposits (e.g. nearshore and floodplain) are more likely to be preserved than upland deposits).
2. Fossils of aquatic organisms, or organisms that find their way into aquatic environments are much more likely to be preserved.
3. Organisms with recalcitrant, and therefore more readily preserved, tissues are more likely to be preserved (e.g. bone, tooth, wood, shell versus, soft bodied organisms).

Question 12

Evolutionary change through time

Answer 12

The environment of planet Earth is spatially variable today (due to relationship with Earth and Sun, it is also temporally variable (seasonal, diurnal).

Environment has also changed over longer periods of time (e.g. the Milankovitch cycles - the axes that Earth spins on changes), or even over vast periods of deep time (i.e. greenhouse, icehouse).

Question 13

Environmental change through time

Answer 13

• Solar luminosity (sun much brighter now)
• Distance between Earth and its moon (tides)
• Continental drift
• Changing atmosphere and climate change (CO2, greenhouse world)
• Milankovitch cycles
• The evolving biota

Question 14

Rare events through time

Answer 14

• Tsunamis
• Super eruptions
• Meteorite impacts
• Mass extinctions (5 large extinctions, when Earth’s biota has been wiped out).

-In 4.6 billion years, rare becomes common, we’ve just never witnessed it.