Lecture 1 Flashcards
Explain fully where the earth started
- 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.
What did the presence of O2 inhibit
Formation of complex organic molecules
What is the central idea of biological evolution
All life on Earth shares a common ancestor
What is speciation
- 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.
What are the 3 branches of speciation
- Parapatry
- Sympatry
- Allopatry
Explain natural selection in evolution
- 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
When can natural selection take place
- 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
What are the patterns of evolution
- Divergent evolution
- Convergennt evolution
- Analogous evolution
Source of a mutation
- 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
Explain homologous structures
- 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
Explain analogous structures
- 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
What does homology indicate
Species belong to related group
What is evolution
- The process that is responsible for the changes in characteristics of species and how new species arise
Explain parallel evolution
- Produces similar characters in related lineages without occurring in a common ancestor
Explain convergent evolution fully
- 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