Flashcards · 9700 · A Level Topic 18

Classification, biodiversity and conservation (A Level) flashcards

19 cards on A Level Topic 18, subtopics 18.1 to 18.3. Pick a subtopic or study them all.

Study mode needs JavaScript. Every card is listed below, so you can still cover the answers and test yourself.

All 19 cards

For a quick read-through or printing. Cover the right-hand side to test yourself.

Biological species concept and one limitation: A species is a group that can interbreed to produce fertile offspring and is reproductively isolated from other species. It cannot be tested on asexual organisms, fossils or separated populations.
Morphological and ecological species concepts: Morphological: organisms share the same structural features (but sexes or larvae may look different). Ecological: organisms occupy the same ecological niche (but niches overlap and vary).
The three domains: Archaea, Bacteria and Eukarya. Archaea and Bacteria are both prokaryotes.
Three differences between Archaea and Bacteria: Membrane lipids: Archaea have ether bonds and branched chains; Bacteria have ester bonds and unbranched fatty acids. rRNA: different base sequences. Cell walls: Bacteria have peptidoglycan; Archaea do not.
Taxonomic hierarchy below domain: Kingdom → phylum → class → order → family → genus → species.
Fungi vs Plantae: Fungi: hyphae or mycelium (yeasts unicellular); chitin walls; heterotrophic, absorbing food after extracellular digestion; store glycogen. Plantae: multicellular; cellulose walls; photosynthesis; store starch.
How are viruses classified?: They are in no domain. They are classified by their nucleic acid (DNA or RNA) and whether it is single- or double-stranded: ssDNA, dsDNA, ssRNA, dsRNA.

Ecosystem and niche: Ecosystem: a relatively self-contained, interacting community of organisms and their environment. Niche: the role of an organism in its ecosystem, including where it lives, what it eats and its interactions with biotic and abiotic factors.
Three levels at which biodiversity is assessed: The range of ecosystems and habitats; the number of species and their relative abundance; genetic variation within each species.
Lincoln index: N = (n₁ × n₂) ÷ m₂, where n₁ = number marked in the first sample, n₂ = total in the second sample, m₂ = marked individuals in the second sample.
Simpson's index of diversity: D = 1 − Σ(n/N)². D near 1: high diversity (many species, evenly spread), more stable. D near 0: one species dominates.
Spearman's rank vs Pearson's correlation: Spearman's: for non-normal or ordinal data; ranks the values. Pearson's: for normally distributed continuous data with a linear pattern. A significant correlation does not prove causation.
Random quadrats vs transects: Random quadrats (random coordinates on a grid) for a uniform area. Line or belt transects for a gradient: a line transect records species touching the line; a belt transect places quadrats along it.

Main causes of extinction: Climate change; competition (often from introduced species); hunting by humans; degradation and loss of habitats.
Roles of zoos in conservation: Captive breeding with breeding records to avoid inbreeding; reintroduction to the wild; research; education.
Frozen zoos and seed banks: Frozen zoos store gametes, embryos and tissue in liquid nitrogen. Seed banks store dried seeds cold, testing germination and regrowing stocks.
Assisted reproduction in endangered mammals: IVF (fertilisation outside the body), embryo transfer into a uterus, and surrogacy, where another female, possibly of a related and more common species, carries the embryo.
IUCN vs CITES: IUCN: assesses conservation status, publishes the Red List and advises governments. CITES: an agreement between governments controlling international trade in endangered species and their products.
Why are invasive alien species controlled?: They compete with, prey on, spread disease to or hybridise with native species, often have no natural predators, change habitats and cause economic damage.