Evolution And Natural Selection Flashcards
(23 cards)
What is evolution?
• A gradual change in the inherited traits within a population over time
• Occurs due to natural selection
Outline the theory of natural selection
- Genetic variation exists due to spontaneous mutations
- Selection pressures (e.g. competition, disease) exist
- Random mutation gives an organism a selective advantage
- Organism is better adapted to the environment and survives
- Organism reproduces, passing on its beneficial alleles
- Frequency of advantageous alleles increase
Describe how antibiotic resistance in bacteria can be
used as an example to illustrate the process of evolution
- Genetic variation exists due to spontaneous mutations
- Antibiotics act as a selection pressure
- Mutations gives a bacterium antibiotic-resistance
- If an antibiotic is administered, the bacterium is better adapted and survives, whilst other bacteria are killed
- Bacterium reproduces, passing on its resistant variant
- Frequency of antibiotic-resistant allele increases
How can the observation of fossils provide evidence for evolution?
• Older fossils (found in rocks deeper in the ground) contain simpler organisms. Newer fossils (found closer to the surface) contain more complex organisms. Comparisons of fossils show that simple organisms evolved into more complex life forms.
• Fossils can be organised into chronological order, allowing the changes in organisms over time to be observed
Describe the role of Darwin in the development of the theory of evolution by natural selection
• Studied a variety of organisms whilst travelling around the world on the HMS
beagle
• Noted that traits can be passed from parents to offspring
• Proposed the idea of ‘survival of the fittest’
• Established the theory of natural selection and published his ideas in ‘On the
Origin of Species’
Describe the role of Wallace in the development of the theory of evolution by natural selection
• He proposed a theory of natural selection that was similar to Darwin’s, although the mechanisms were different
• He gathered greater evidence (e.g. studying warning colouration in butterflies) to support the theory
What fossils have provided evidence for human evolution?
• ‘Ardi’ - 4.4 million years old (ardipethicus ramidus)
• ‘Lucy’ - 3.2 million years old. (australiopethicus africanus)
• Leakey discovered 1.6 million year old fossils
How has the development of stone tools provided evidence for evolution?
• Correlation between the development of more complex tools and an increase in brain size
• Primitive tools are older than more complex tools. Brain size has increased over time .. as brain size increased, advancements in tool use were made.
Describe the methods used by scientists to date tools
• Carbon-14 dating - estimating the age of carbon-containing material that is found in tools (e.g. wooden handles) or alongside tools (e.g. fur)
• Stratigraphy - using the age of the layers of sediment surrounding the tool as an indication of the age of the tool
What is a pentadactyl limb?
How does the pentadactyl limb provide evidence for evolution?
A limb with five digits present in animals, bird, reptiles and amphibians
The presence of the pentadacty! limb suggests that all species which possess it have descended from a common ancestor.
What is classification?
The organisation of organisms into groups
What is taxonomy?
The classification of organisms into taxa: kingdom, phylum, class, order, family, genus, species.
Name the five kingdoms
Animals, plants, fungi, protists, prokaryotes
Describe the three domains system of classification
• Organisms are initially divided into an extra three groups: Archaea, Bacteria, Eukarya
• domain, kingdom, phylum, class, order, family, genus, species.
What is selective breeding
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
Outline the main steps involved in selective breeding
- Identify a desired characteristic e.g. disease resistance
- Select parent organisms that show the desired traits and breed them together
- Select offspring with the desired traits and breed them together
- Process repeated until all offspring have the desired traits
What is the main advantage of selective breeding?
Creates organisms with desirable features:
• Crops produce a higher yield of grain
• Cows produce a greater supply of milk
• Plants produce larger fruit
• Domesticated animals
Outline the disadvantages of selective breeding (4)
• Reduction in the gene pool (which becomes especially harmful if sudden environmental change occurs)
• Inbreeding results in genetic disorders
• Development of other physical problems e.g. respiratory problems in bulldogs
• Potential to unknowingly select harmful recessive alleles
What is genetic engineering?
• The modification of the genome of an organism by the insertion of a desired gene from another organism
• Enables the formation of an organism with beneficial characteristics
Describe the process of genetic engineering
- DNA is cut at specific base sequences by restriction enzymes to create sticky ends
- Vector DNA cut using the same restriction enzymes to create complementary sticky ends
- Ligase enzymes join the sticky ends of the DNA and vector DNA
forming recombinant DNA - Recombinant DNA mixed with and ‘taken up’ by target cells
Describe the benefits of genetic engineering
• Increased crop yields for growing population e.g. herbicide-resistance, disease-resistance
• Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk
• GM crops produce scarce resources e.g. GM golden rice produces beta-carotene (source of vitamin A in the body)
Describe the risks of genetic engineering (4)
• Long-term effects of consumption of GM crops unknown
• Negative environmental impacts e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming ‘superweeds’
• Late-onset health problems in GM animals
• GM seeds are expensive. LEDCs may be unable to afford them or may become dependent on businesses that sell them.
How is genetic engineering used to protect crops against insects?
• The gene for toxin production in Bt can be isolated and inserted into the DNA of crops
• Bt crops now secrete the toxin which kills any insect larvae that feed on it
