Lecture 1

Question 1

Explain fully where the earth started

Answer 1

• Earth and other planets formed about 4.6 billion years ago
• The earth cooled enough to form a crust 4.2 to 4.1 BYA. Surface temperature ranged from 500 to 1000deg Celsius
• Earth originally had primitive atmosphere
  H2O, N2, CO2, H2 & CO were the gasses present.
• It was a reducing atmosphere lacking free O2
• The geological time scale in the next slide gives us a good idea of when life started and when oxygen was introduced into the atmosphere.

Question 2

What did the presence of O2 inhibit

Answer 2

Formation of complex organic molecules

Question 3

What is the central idea of biological evolution

Answer 3

All life on Earth shares a common ancestor

Question 4

What is speciation

Answer 4

• It is the splitting of one species in to two or more species, or the transformation of one species into a new species over time.
• It is the final result of changes in the in gene pool allele and genotype frequencies
• The one requires geographic isolation while the other one does not.

Question 5

What are the 3 branches of speciation

Answer 5

• Parapatry
• Sympatry
• Allopatry

Question 6

Explain natural selection in evolution

Answer 6

• The mechanism by which species change over time –some of this was discussed by Darwin
• Inheritance of acquired characteristics-Lamarck is a name that comes to mind
  • This deals with modifications in an individual caused by its environment or disuse of a structure –it could be inherited by its offspring-causing a change in a species

eg ) Finches from Galapagos Archipelago

Question 7

When can natural selection take place

Answer 7

• Natural selection can only take place if there is variation among individuals in a population.
• Genetic diversity in a population has two sources: Mutation and sexual reproduction

Question 8

What are the patterns of evolution

Answer 8

• Divergent evolution
• Convergennt evolution
• Analogous evolution

Question 9

Source of a mutation

Answer 9

1. A mutation can affect the phenotype that may cause reduced fitness- resulting in fewer offspring.
2. Mutation may produce a phenotype with a beneficial effect on fitness
3. Neutral mutations that have no effect on fitness

Question 10

Explain homologous structures

Answer 10

• Are related to each other through common descent but may differ in structure and function

e.g) the forelimbs of a horse and the wings of a bat

Question 11

Explain analogous structures

Answer 11

• Have the same function but not derived from the same organ in a common ancestor

e.g. the wings of an insect and the wings of a bat

Question 12

What does homology indicate

Answer 12

Species belong to related group

Question 13

What is evolution

Answer 13

• The process that is responsible for the changes in characteristics of species and how new species arise

Question 14

Explain parallel evolution

Answer 14

• Produces similar characters in related lineages without occurring in a common ancestor

Question 15

Explain convergent evolution fully

Answer 15

• Similar biological traits evolves in two unrelated species as a result of exposure to similar environments. Eg Wings of birds and wings of bats
• Acquisition of similar trait in distantly related lines of descent as a result of adaptation to similar environmental conditions

Question 16

Explain adaptive radiation

Answer 16

When a single ancestral species rapidly gives rise to a radiation of new species as each adapts to a specific environment

Eg ) The Galapagos finches

Question 17

What is macroevolution

Answer 17

• Is part of the history of life on earth and involves speciation
• Speciation involves the splitting of one species into two or more species

Question 18

What are the 3 concepts of species

Answer 18

• Morphological species concept
• Evolutionary species concept
• Phylogenetic species concept

Question 19

Explain each of the 3 concepts of species

Answer 19

• Morphological species concept: Species identified on the basis of appearance or morphology
• Evolutionary species concept: Species differentiated on the basis a specific evolutionary pathway
• Phylogenetic species concept: A species is the smallest set of interbreeding organisms-usually a population, shares a common ancestor

Question 20

What are reproductive isolating mechanisms

Answer 20

Two major operators that makes sure that species remain separate

Question 21

Explain prezygotic isolators

Answer 21

• Habitat isolation
• Temporal – time differences in mating strategy
• Behavioural – courtship differences
• Mechanical – incompatible reproductive organs
• Gamete – gametes not able to form zygote

Question 22

Explain postzygotic isolating mechanisms

Answer 22

• Prevents hybrid offspring from reproducing
• Zygote may be formed but hybrid zygote not able to undergo mitosis
• Hybrid zygote may develop into sterile adult. Gamete formation prevented during meiosis
• F2 fitness-offspring are fertile but F2 generation is sterile

Question 23

Explain the cenozioc era

Answer 23

• This is the present era. Mammals diversified and human evolution commenced
• Three periods: Palaeogene and Neogene and Quartenary
• Mammalian diversification
• Evolution of Primates

Question 24

Explain the paleozoic era

Answer 24

• Era lasted 300 million years
• All extant (living) taxa trace origins to Cambrium or earlier
• Richness due to development of external skeletons eg. Trilobites

Question 25

Explain the precambrium

Answer 25

- History of life is divided into Eras, Periods, Epochs - Oldest biological era is the Precambrium - Lasted 87% of geological time 4.5 BYA - formation of Earth 3.5 BYA – Oldest known fossils 2.5 BYA – O2 accumulates in atmosphere 2.0 BYA – Oldest eukaryote fossils 1.4 BYA – Protists evolve and diversify 600 MYA – Ediacarian animals 543 MYA – Cambrium animals

Question 26

Explain allopatric speciation fully

Answer 26

- Speciation by geographic isolation - Something extrinsic to the organisms prevents two or more groups from mating with each other regularly, eventually causing that lineage to speciate. - Isolation might occur because of great distance or a physical barrier, such as a desert or river.

Question 27

Explain allopatric speication and gene flow

Answer 27

- Can occur even if the barrier is a little “porous,” that is, even if a few individuals can cross the barrier to mate with members of the other group. - In order for a speciation even to be considered “allopatric,” gene flow between the soon-to-be species must be greatly reduced making mating impossible

Question 28

Explain parapatric speciation fully

Answer 28

- No specific extrinsic barrier to gene flow. - The population is continuous, yet population does not mate randomly. - Individuals more likely to mate with geographic neighbours than with individuals in a different part of the population’s range. - Divergence may happen due to reduced gene flow within the population and varying selection pressures aross the population’s range. eg ) The grass species Anthoxanthum odoratum

Question 29

Explain sympatric speciation

Answer 29

- Large-scale geographic distance not required to reduce gene flow between parts of a population. - How? Ability to exploit a new niche may automatically reduce gene flow with individuals exploiting another niche. Example, herbivorous insects try out a new host plant.

Question 30

Explain examples of sympatric speciation

Answer 30

- Fish of lake Malawi – Fish in different parts of the lake evolved to become different species. - They end up occupying different parts of the lake and feed on different types of organisms. - Adaptive radiation through ecological release. Species evolve because of competition for food and resources

Question 31

Explain autoploidy and allopdoidy in plants

Answer 31

- Autoploidy: small diploid seeded bananas produces diploid gametes because of nondisjunction. They would then produce a polyploidy which is sterile - Alloploidy: Reproduction between two species of plants to produce a sterile hybrid. Doubling of this chromosome number produce a fertile 3rd species, that can only breed with itself.

Question 32

Explain the factors influencing evolution

Answer 32

- Continental drift The earth’s crust divided into tectonic plates that move because of seafloor spreading at ocean ridges - Mass extinctions Caused by climatic changes after meteoric events and/or after continents drift into new positions - Domestication Human induced selection of plants and animals (think of cattle, grains, dogs) - Vicariant events Are speciation events where a species' distribution becomes segmented and the separated populations evolve due to different selecting factors, causing the populations to become unique species

Question 33

Expalin examples of vicariant events

Answer 33

- The present day continental masses of Australasia, Antarctica, Africa, Madagascar, India and South America were once a great, single continent that geologists call Gondwanaland or Gondwana.  - Evidence of the Gondwanaland connection is still seen in some of the living flora and fauna of those land masses