5.4 Flashcards
Define gene mutations
Change in the DNA base sequence due to the addition, deletion or substitution of a base
Outline the process of evolution through natural selection
Selection pressure will cause competition between individuals
Natural mutations within population may lead to advantageous alleles
Individuals out-competed
Those with advantageous alleles will survive and reproduce
Passing on advantageous alleles
Increased allele frequency within a population
What are the 4 forms of evidence for evolution
Geographical distribution
Fossil records show gradual change over time
Molecular evidence - genomics and proteomics
Phylogeny diagrams compare amino acid sequences
How is the idea of a common ancestor supported
Organisms share common proteins such as ribosomes and DNA polymerase
What is speciation
If natural selection happens to a population that is reproductively isolated, a new species can form
What does reproductively isolated mean
Individuals can no longer breed to produce fertile offspring
What happens during geographical isolation
Some of the population moves from the mainland to an island
The island popularity is now geographically isolated from the mainland population and undergoes natural selection to evolve into a new species
Evolution through natural selection
Describe what is meant by geographical isolation
Populations are isolated by a physical barrier which leads to different selection pressures
Describe what is meant by ecological isolation
Species occupy different parts of the same habitat
Describe what is meant by temporal isolation
Species exist in the same area but reproduce at different times
Describe what is meant by behavioural isolation
Species exist in the same area but do not respond to each other’s courtship behaviour
Describe what is meant by physical incompatibility isolation
Species coexist but there are physical reasons which prevent them copulating
E.g. Incompatible gametes or genitalia
Describe what is meant by hybrid incompatibility isolation
Hybrids are produced but they don’t survive long enough to breed
Describe what is meant by hybrid sterility isolation
Hybrids survive to reproductive age but cannot reproduce
What are the two most likely reasons for rising CO2 levels
Deforestation and the combustion of fossil fuels
How does deforestation contribute to rising CO2 levels
Trees and peat bogs act as carbon sinks
Burning of trees also burn peat bogs
Cutting of trees releases carbon
As carbon is stored for thousands of years, large a,punts are released
How does combustion contribute to rising CO2 levels
Fossil fuels made from partially decomposed animals and plants
Through the process of fossilisation
These organic compounds contain carbon and when they are burnt, the carbon is released
How do other factors contribute to rising CO2 levels
Volcanoes release CO2
Erosion processes release it from sediments in the ocean
Increase in acid rain increases rate at which CO2 is released via erosion
Rising global temperature can have an effect
What two factors maintain the balance of the carbon cycle
Reforestation and biofuels
What is a biofuel
any energy source produced, directly by plants or indirectly by animals, in recent photosynthesis
What two main properties do biofuels have
they are renewable and carbon-neutral
Give four examples of biofuels
wood, straw, beg oil, ethanol and methane
What are 1st generation biofuels
made directly from food crops
What are 2nd generation biofuels
manufactured from various types of biomass
What are the three main disadvantages to biofuels
Destruction of forests for palm oil
Affects food availability
CO2 released from transportation and machinery
How does reforestation help maintain the balance of the carbon cycle
young, new trees are net absorbents of CO2
they grow rapidly and there is little decay, therefore respiration rates will be lower than photosynthesis rates
What are the three main disadvantages of reforestation
upper limit for tree growth
land availability is limited
reduces water availability for forests
