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Flashcards · H420 · Topic 4
Biodiversity, evolution and disease flashcards
17 cards on Topic 4, subtopics 4.1.1 to 4.2.2. Pick a subtopic or study them all.
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4.1.1 Communicable diseases, disease prevention and the immune system
- Pathogen types with one plant and one animal disease each
- Bacterium: ring rot; tuberculosis. Virus: Tobacco Mosaic Virus; HIV/AIDS, influenza. Protoctist: potato and tomato late blight; malaria. Fungus: black sigatoka; athlete's foot.
- Plant defences against pathogens
- Chemicals (terpenoids, phenols, alkaloids, defensins, chitinase); callose deposited in plasmodesmata and sieve plates to block spread; lignin and thicker walls; the hypersensitive response; stomatal closure.
- How does a blood clot form?
- Platelets release substances at the damaged vessel, starting a cascade of reactions. Soluble fibrinogen is converted to insoluble fibrin, whose threads form a mesh that traps platelets and red blood cells.
- Opsonins, agglutinins and anti-toxins
- Opsonins coat a pathogen so phagocytes bind and engulf it more easily. Agglutinins clump pathogens using their two binding sites. Anti-toxins bind toxins so they cannot bind target cells.
- Plasma cell vs B memory cell; T helper vs T killer
- Plasma cell secretes antibody now; memory cell is long-lived and waits for a secondary response. T helper releases cytokines (interleukins) that activate B cells and T killers; T killer destroys infected body cells.
- Autoimmune disease
- The immune system attacks the body's own cells because self and non-self are not distinguished. Example: rheumatoid arthritis, in which joint tissues are attacked.
- Herd immunity: proportion that must be immune
- So many people are immune that spread is limited, protecting those who cannot be vaccinated. Simple model: proportion immune needed = 1 − 1/R₀ (R₀ = 4 needs 75 %).
4.2.1 Biodiversity
- Species richness vs species evenness
- Richness: the number of different species in a habitat. Evenness: how similar the numbers of individuals of each species are. Species biodiversity includes both.
- Simpson's Index of Diversity for counts of 10, 5, 3 and 2
- N = 20. n/N = 0.5, 0.25, 0.15, 0.1. Squares sum to 0.25 + 0.0625 + 0.0225 + 0.01 = 0.345. D = 1 − Σ(n/N)² = 1 − 0.345 = 0.655.
- Random, systematic and stratified sampling
- Random: random-number coordinates; for a uniform area. Systematic: regular intervals, such as a transect; for a gradient. Stratified: each distinct zone sampled in proportion to its size.
- In situ vs ex situ conservation, with examples
- In situ: in the natural habitat, such as wildlife reserves and marine conservation zones. Ex situ: away from it, such as zoos (captive breeding), botanic gardens and seed banks.
4.2.2 Classification and evolution
- Bacteria vs Archaea vs Eukarya
- Bacteria: peptidoglycan wall, ester-linked lipids, no histones. Archaea: no peptidoglycan, ether-linked branched lipids, DNA with histones. Both: no nucleus, 70S ribosomes. Eukarya: nucleus, 80S ribosomes, linear DNA with histones.
- Why is the binomial system useful?
- It is universal: the same two-part name (genus, then species) is used worldwide, avoiding confusion over common names. A shared genus shows a close relationship.
- Mechanism of natural selection
- Variation exists (mutation, sexual reproduction). A selection pressure acts. Individuals with advantageous alleles are more likely to survive and reproduce, passing the alleles on, so the allele frequency rises over generations.
- Intraspecific vs interspecific variation
- Intraspecific: differences between individuals of the same species. Interspecific: differences between different species.
- Anatomical, physiological and behavioural adaptations
- Anatomical: structural features, such as the rolled leaves of marram grass. Physiological: processes in the body, such as a lowered metabolic rate in hibernation. Behavioural: actions, such as migration or courtship.
- Evidence for the theory of evolution by natural selection
- Palaeontology (the fossil record), comparative anatomy (homologous structures such as the pentadactyl limb) and comparative biochemistry (differences in DNA base sequences and in proteins such as cytochrome c). Darwin and Wallace proposed the theory.