Topic 4

• What is evolution?

  The gradual change in a species over time due to natural selection
• Outline the theory of natural selection

  1. Genetic variation exists due to spontaneous mutations

  2. Selection pressures (e.g. competition, disease) exist

  3. Random mutation gives an organism a selective advantage

  4. Organism is better adapted to the environment and survives

  5. Organism reproduces, passing on its beneficial alleles

  6. Frequency of advantageous alleles increase
• Why does competition between organisms in a habitat exist

  The resources within a habitat required for survival are limited
• Give some examples of competition between organisms within a habitat

  Competition between animals for food, shelter, mates etc.

  Competition between plants for light, water, minerals etc.
• Describe how antibiotic resistance in bacteria can be used as an example to illustrate the process of evolution

  1. Genetic variation exists due to spontaneous mutations

  2. Antibiotics act as a selection pressure

  3. Mutations gives a bacterium antibiotic-resistance

  4. If an antibiotic is administered, the bacterium is better adapted and survives, whilst other bacteria are killed

  5. Bacterium reproduces, passing on its resistant variant

  6. Frequency of antibiotic-resistant allele increases
• Why is the development of antibiotic resistance in bacteria a good study for evolution

  Bacteria reproduce very rapidly, allowing the first-hand observation of evolution
• 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
• How has the theory of evolution by natural selection impacted modern biology and society?

  ● Enables the classification of organisms into taxa

  ● Influences modern medicine by emphasising the importance of finishing antibiotic treatments and the need for the constant production of new antibiotics

  ● Highlights the importance of high genetic diversity in habitats which aids conservation projects
• What fossils have provided evidence for human evolution?

  ● 'Ardi' - 4.4 million years old

  ● 'Lucy' - 3.2 million years old

  ● Leakey discovered 1.6 million year old fossils
• What clues does 'Ardi' give scientists about human evolution

  Female hominid fossil. She shows phenotypic traits which encompass characteristics of both humans and apes

  Ape like characteristics

  Human like characteristics
• What clues does Lucy give scientists about human evolution

  Female hominid fossil. She shows phenotypic traits which are more human-like than that of 'Ardi':

  ● The structure of bones in her legs and feet are more adapted to walking than climbing

  ● However, her brain size is closer to that of an ape's
• How did Leakey's findings provide evidence for human evolution?

  He discovered many hominid fossils.

  The 1.6 million year old fossil 'Turkana Boy' showed traits comparable to that of modern-day humans e.g. similar brain size.
• 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?

  A limb with five digits present in animals, bird, reptiles and amphibians
• How does the pentadactyl limb provide evidence for evolution?

  The presence of the pentadactyl limb suggests that all species which possess it have descended from a common ancestor.
• What is classification?

  Organisation of living 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
• What happens to the number of organisms in each taxon as you move down the hierarchy?

  The number of organisms in each taxon group decreases
• Traditionally, organisms were grouped based on similarities and differences in their anatomy and behaviour. What is the problem with this?

  ● Organisms that are not closely related may look alike and behave similarly if they live in the same environment e.g. sharks and dolphins

  ● Some closely related species may look very different if they live in different habitats e.g. queen ants, worker ants
• What advancements in science have led scientists to reconsider the five kingdoms classification system?

  ● Microscopes

  ● Biochemistry

  ● DNA and RNA analysis
• 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.
• Which domain do eukaryotic organisms belong to

  Eukarya
• What domains do prokaryotes belong to?

  Bacteria and Archaea
• Describe Domain Bacteria

  Consists of true bacteria e.g. E.coli
• Describe Domain Archaea

  ● Consists of primitive microorganisms

  ● Contains extremophiles - adapted to live in extreme conditions e.g. hot springs
• 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

  1. Identify a desired characteristic e.g. disease resistance

  2. Select parent organisms that show the desired traits and breed them together

  3. Select offspring with the desired traits and breed them together

  4. 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
• Other than in agriculture, where else is selective breeding useful?

  ● In medical research

  ● In sports e.g. horse racing
• 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.
• How can plants be cloned?

  ● Taking plant cuttings

  ● Tissue culture
• What is tissue culture?

  A method of growing living tissue in a suitable medium
• Describe how plants are grown using tissue culture

  1. Select a plant that shows desired characteristics

  2. Cut multiple small sample pieces from meristem tissue

  3. Grow in a petri dish containing growth medium

  4. Transfer to compost for further growth
• What must be ensured when preparing tissue cultures?

  Ensure aseptic conditions to prevent contamination by microorganisms
• What does the growth medium contain

  Nutrients and growth hormones
• What are the advantages of growing plants by tissue culture

  ● Fast and simple process.

  ● Requires little space.

  ● Enables the growth of many plant clones with the same desirable characteristics.

  ● Useful in the preservation of endangered plant species.