Define interspecific variation:
Variation between members of different species.
Define intraspecific variation:
Variation between organisms within a species.
What are the two causes of variation?
- Genetic
- Environmental
What are the genetic causes of variation?
- alleles
- mutations
- meiosis - independent assortment and “crossing over”
- chance - random fertilisation
What are the three main categories of adaptations?
- anatomical
- behavioural
- physiological
Examples of anatomical adaptations:
- body coverings - can provide warmth and protection
- camouflage - protection from predators
- teeth - teeth are adapted to determine animal’s diet
- mimcry - protection from predators
What is an example of an adapted species we have covered?
Marram grass
Examples of behavioural adaptations:
- survivial behaviours
- courtship - increases chances of reproduction
- seasonal behaviours - migration / hibernation
Which two catagories do behavioural adaptations fall into?
Innate - ability is inherited through genes
Learned - adaptations learnt thorugh experience or from observing other animals
Examples of physiological adaptations:
- poision production
- antibiotic production (by bacteria)
- water holding
Define evolution:
A change in inherited characteristics of a group of organisms over time
What is a convergent evolution?
Where unrelated species have evolved to share similar traits due to similar environments or selection pressures.
e.g. marsupials vs placental mammals
What is divergent evolution?
The evolution of different species from a common ancestor, each with a different set of adaptive features.
- opposite of convergent evolution
What evidence is there for evolution?
- paleontology (study of fossils)
- comparitive anatomy
- comparitive biochemistry
Explain how paleontology is evidence for evolution:
- fossils of the simplest organisms - found in oldest rocks. More complex organisms are found in newer rock.
- the sequence in which organisms are found match their ecological links.
- anatomy of fossil organisms show how closely organisms have evolved from common ancestors.
What are analogous structures?
Very different structures which perform the same role.
They have the same function but a very different genetic origin e.g. fish and whale fins.
What is a homologous structure?
A structure that appears superficially different but has the same underlying structure.
- opposite of analogous structures
What is comparitive biochemistry?
The study of similarities and differences in proteins & other molecules that control life processes.
Which molecules are usually studied in comparitive biochemistry?
- cytochrome c
- ribosomal RNA
What are selection pressures?
Factors that affect an organism’s chances of survival or reproductive success.
Explain the steps of natural selection (6):
- Organisms in a species show variation in their characteristics - caused by genetic variation and different alleles of genes.
- Organisms with characteristics best suited to their selection pressures are more likely to survive and reproduce.
- Successful organisms pass on the alleles encoding the advantageous characteristic to their offspring.
- Process repeats over generations - over time, allele frequency of the advantageous allele increases in the population’s gene pool.
- Over many generations, this can lead to the evolution of a new species.
