Lecture 1 Flashcards
1
Q
Explain fully where the earth started
A
- 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.
2
Q
What did the presence of O2 inhibit
A
Formation of complex organic molecules
3
Q
What is the central idea of biological evolution
A
All life on Earth shares a common ancestor
4
Q
What is speciation
A
- 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.
5
Q
What are the 3 branches of speciation
A
- Parapatry
- Sympatry
- Allopatry
6
Q
Explain natural selection in evolution
A
- 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
7
Q
When can natural selection take place
A
- 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
8
Q
What are the patterns of evolution
A
- Divergent evolution
- Convergennt evolution
- Analogous evolution
9
Q
Source of a mutation
A
- A mutation can affect the phenotype that may cause reduced fitness- resulting in fewer offspring.
- Mutation may produce a phenotype with a beneficial effect on fitness
- Neutral mutations that have no effect on fitness
10
Q
Explain homologous structures
A
- 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
11
Q
Explain analogous structures
A
- 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
12
Q
What does homology indicate
A
Species belong to related group
13
Q
What is evolution
A
- The process that is responsible for the changes in characteristics of species and how new species arise
14
Q
Explain parallel evolution
A
- Produces similar characters in related lineages without occurring in a common ancestor
15
Q
Explain convergent evolution fully
A
- 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
16
Q
Explain adaptive radiation
A
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
17
Q
What is macroevolution
A
- Is part of the history of life on earth and involves speciation
- Speciation involves the splitting of one species into two or more species
18
Q
What are the 3 concepts of species
A
- Morphological species concept
- Evolutionary species concept
- Phylogenetic species concept
19
Q
Explain each of the 3 concepts of species
A
- 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
20
Q
What are reproductive isolating mechanisms
A
Two major operators that makes sure that species remain separate
21
Q
Explain prezygotic isolators
A
- Habitat isolation
- Temporal – time differences in mating strategy
- Behavioural – courtship differences
- Mechanical – incompatible reproductive organs
- Gamete – gametes not able to form zygote
22
Q
Explain postzygotic isolating mechanisms
A
- 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
23
Q
Explain the cenozioc era
A
- This is the present era. Mammals diversified and human evolution commenced
- Three periods: Palaeogene and Neogene and Quartenary
- Mammalian diversification
- Evolution of Primates
24
Q
Explain the paleozoic era
A
- Era lasted 300 million years
- All extant (living) taxa trace origins to Cambrium or earlier
- Richness due to development of external skeletons eg. Trilobites
25
Explain the precambrium
- 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
26
Explain allopatric speciation fully
- 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.
27
Explain allopatric speication and gene flow
- 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
28
Explain parapatric speciation fully
- 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
29
Explain sympatric speciation
- 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.
30
Explain examples of sympatric speciation
- 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
31
Explain autoploidy and allopdoidy in plants
- 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.
32
Explain the factors influencing evolution
- 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
33
Expalin examples of vicariant events
- 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
