Topic 3.2 Natural Selection Flashcards
Define natural selection
the process by which the organisms that are best adapted in a particular environment are most likely to survive and reproduce, passing on their advantageous alleles to their offspring
Why does natural selection occur?
- predation
- disease
- competition
all resulting in differential survival and reproduction
Explain how natural selection results in the development of new characteristics
- random mutations result in new alleles
- some alleles give the organism an advantage over the rest of the species, making them more likely to survive and reproduce
- their offspring receive the new allele, and frequency continues to increase over many generations
What are the 3 types of adaptation?
- anatomical (changes to body structure) e.g. oily fur
- physiological (changes to body processes) e.g. venom production
- behavioural (changes to actions) e.g. hibernation
What’s a genotype?
the genetic make-up of an organism with respect to a particular feature
What’s a phenotype?
the physical traits (including biomechanical characteristics) expressed as a result of the interactions of the genotype with the environment
Define allele
an allele is a version of a gene, a variant
What is ecology?
the study of the interactions of organisms with each other and with the environment in which they live
Define a niche
the role of an organism within the habitat in which it lives, species sharing the same niche will compete with each other
Define speciation
the formation of a new species
What is allopatric speciation?
speciation that takes place when populations are physically and geographically separated and there can be no interbreeding or gene flow between the populations
What is sympatric speciation?
speciation that takes place between populations of a species living in the same place. They become reproductively isolated by mechanical, behavioural or seasonal mechanisms and gene flow continues between the populations to some extent as speciation takes place
How does speciation occur?
when a population is split and reproductively isolated, there are different selective pressures on the 2 groups. if the genetic makeup changes to the extent that the 2 groups can’t interbreed, they have become separate species
How does evolution relate to bacteria resistance?
bacteria can develop mutations that make them resistant to antibiotics, which they will then pass on when they reproduce
Name the different types of isolation (5)
- geographical
- ecological
- seasonal
- behavioural
- mechanical
Define geographical isolation
occurs when a physical barrier e.g. river or mountain range separates individuals from an original population
What is ecological isolation?
occurs when 2 populations inhabit the same region, but develop preferences for different parts of the habitat
Define seasonal isolation
occurs when the timing of flowering or sexual receptiveness in some parts of the population drifts away from the norm of the group, which can eventually lead to the groups reproducing months apart
What is behavioural isolation?
happens when changes occur in the courtship ritual, display or mating pattern so that some animals do not recognise others as being potential mates, which may be due to mutations causing changes in markings e.g. colour or pattern
What is mechanical isolation?
happens when a mutation occurs that changes the genitalia of animals making it physically impossible for them to mate successfully, or it changes the relationship between the stigma and stamens
State the 4 concepts of the theory of evolution
- living organisms that reproduce sexually show great variety in their appearance
- organisms produce an excess of offspring so there is always a struggle to survive which means there is competition between the same species
- advantageous characteristics are passed down to offspring
- organisms that inherit disadvantageous characteristics are likely to die before reproducing
