NATURAL AND ARTIFICIAL SELECTION Flashcards
What are Darwins four observations?
Species over reproduce
Populations tend to remain fairly constant
Variation within a species
Offspring often resemble their parents- characteristics are passed on
What are Darwins deductions?
- struggle for survival- individuals get eaten, diet disease or competition for resources
- individuals with best characteristics that best adapt them for their environment are most likely to survive and reproduce
- if characteristics can be inherited then organisms will pass them onto their offspring (passing of ALLELES)
Who was Wallace?
Independently came to the same conclusions as Darwin
Made collections in the Amazon and South East Asia
Darwin and Wallace both published joint papers on evolution and natural selection
How are fossil records evidence for evolution?
Show diff species were alive in the past
Become extinct and new species have arisen
Fossilised remains show species getting more and more complex (while retaining similarities)
Can be used on phylogenetic trees
What are problems with fossil records?
Often incomplete
Only hard parts fossilise and many organisms don’t have hard parts
Only form under certain circumstances
Can be damaged by movement of rocks
How are biological molecules evidence for evolution?
Many bio molecules found in all organisms- suggesting all species arose from one common ancestor
Closely related species have more similarities
How is protein variation evidence for evolution?
Vital proteins, DNA and RNA, four in all organisms
Higher organisms have added sub units that improve regulation
Cytochrome C (protein used in respiration) show patterns of changes
-more change= more evolutionary distance
How is DNA evidence for evolution?
Sequencing the bases in DNA allows for comparison, the more differences found means that there is greater evolutionary distance
How is mitochondrial DNA evidence for evolution?
Mitochondria passes to offspring by the egg (female) during sexual reproduction
Mutations more common in mitochondrial DNA than genomic DNA
Variations used to trace human evolution
Define an adaption
A feature that enhances survival and long-term reproductive success
Well adapted organisms should be able to..
Find enough food/photosynthesise at a fast enough rate
Defend against predators and disease
Survive physical conditions of environment, e.g. temp, water availability
Respond to changes in the environment
Reproduce successfully
Define behavioural adaption
Aspect of behaviour of the organism that allows it to survive where it lives
Examples of behavioural adaptions
Survival behaviour- opossum plays dead
Courtship- attract a mate
Seasonal behaviour- migration, hibernation
Define physiological adaption
Internal and biochemistry ical features that ensure the correct functioning of cell processes
Examples of physiological adaptions
Poison production to kill prey
Antibiotic production- some bacteria produces e antibiotics to kill other species
Define anatomical adaptions
Any structure that enhances survival of the organism (physical features)
Examples of anatomical adaptions
Body covering- scales, hairs
Teeth- carnivores= sharp teeth, herbivores= continuously growing molars
What is convergent evolution?
Adaptions controlled by the environment
Meaning evolutionary distinct species that live in similar habitats, or exploit similar ecological niche, often evolve similar adaptions
What is an example of convergent evolution?
Marsupial and Placental moles
Powerful front claws, hairs on face, independently evolved
Natural selection:
Explain genetic variation
Random mutations cause different alleles of genes
Instraspecific variation
Occasionally new alleles are beneficial, increase alleles frequency
Natural selection:
Explain selection pressures
Organisms have to compete for survival Environmental factors confer greater chance of survival and more reproduction examples: -availability of food -predators -disease
Natural selection:
Explain reproductive success
Best adaptions most likely to survive and reproduce
Pass on alleles that code for beneficial characteristics to their offspring
Natural selection:
Repeated over many years
Repeated so beneficial alleles become more frequent in the population
Proportion of population with advantageous characteristics increase
How is pesticide resistance an example of implication of evolution for human populations?
Creates a selection pressure for those with some form of resistance to insecticides
Problem because many insects carry disease therefore infection rates climb, pesticide become concentrated in the food chain
What is stabilising selection?
If enviro stable, stabilising selection occurs
Same alleles selected in every successful generation and the gene pool of a population;ation remains roughly the same
Examples:
Coats of mice in forest best colour suited to enviro
What is directional selection?
If enviro changes there will be a change in the selection pressure on the population
DS evolutionary force of natural selection
One extreme selected against another will have selective advantage
Over time allele frequency shifts towards an extreme
E.g. Londons peppered moths- industrial period, became black
What is genetic drift?
Random fluctuations can occur in allele frequency within a population- purely by chance
Most likely in small populations
Occurs due to randomness of reproduction
Extreme cases alleles can be eradicated from population
What is genetic bottleneck?
Population decreases which decreases allele frequency which decreases variation/genetic diversity
What is the founder effect?
New population started from. a few individuals, may show loss of genetic variation
Amish people descended from small number of people and suffer from genetic disorders
Formula for proportion of polymorphic gene loci
Number of polymorphic gene loci/total number of loci
Define speciation
Large populations can be split into sub-groups by an isolating mechanism, geographical or reproductive barrier
Explain geographical isolation
Physical barriers can separate population into two breeding groups
Diff selection pressures will act as diff populations
Selection, genetic drift and mutation will lead to diff gene frequencies in two populations
ALLOPATRIC SPECIATION
Explain reproductive isolation
Two groups of organism may be isolated from breeding together even if they live in the same place Reasons: -mechanical problems (e.g. diff sizes) -gamete incapability SYMPATRIC SPECIATION
Explain ecological barriers as reproductive isolation
Two groups may live in the same area but rarely meet
Explain temporal/seasonal barriers as reproductive isolation
Two groups may live in the same habitat but may not be active at the same time of year or day
Differences between natural and artificial selection
Slow, fast
Benefits species, benefits humans
Whole genotype selected, few traits selected
Explain a dairy cow as an example of artificial selection
Select cows with high milk yields to reproduce
Bulls which have progeny with high milk yields are used
Repeated over many generations
Artificial insemenation used to maximise no. of cows bulls can fertilise
What are problems with artificial selection
Reduces genetic diversity/variation
Interbreeding often occurs increased chance of two recessive alleles coming together
Characteristics selected may cause health problems for organism
What are solutions to artificial selection problems
Breeders may cross two different varieties to increase hybrid vigour
Gene banks created including ‘wild types’
