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Unit 3 Biology

Booklet 2

What is biodiversity? The varitey and relative abundance of a species.
What is extinction? A natural process which leads to the complete demise of a species.
what is a mass extinction? When a large proportion of a species becomes extinct over a short geological time period.
What does fossil evidence indicate? That there have been several mass extinction events in the past.
What have mass extinctions been linked to? Changes in climate.
What happens to biodiversity following a mass extinction event? It regains and increases slowly. This is due to speciation of survivors. Over time surviving species spread out filling unoccupied / vacant niches.
What are megafauna? animals that are larger thatn humans
What is an example of megafauna from the past? Woolly Mammoth.
Why were the mass extinction of megafauna correlated with the spread of humans across the planet? They were targets of overhunting and had slow reproduction rates so were susceptible to extinction.
Why is it difficult to state precise extinction rates for past mass extinctions? The fossil record is incomplete (doesn't represent particular age, abundance, when a species was present.
Why is it difficult to state the current extinction rates? Because many species have not been discovered / identified yet.
What is causing the currently escalating rate of ecosystem degradation? Human activities (deforestation, overhunting,overfishing, burning of fossil fuels, expansion of urban areas.
What do human activities (overhunting etc cause? The rate of species extinction to be much higher than the natural background rate.
What are the 3 measurable components of biodiversity? Genetic diversity, Species diversity, Ecosystem diversity.
What is genetic diversity? The genetic variation in a population (represented by the number and frequency of alleles)
What is the importance of genetic diversity? Indicates the total number of genetic characteristics of a species.
What does low genetic diversity lead to? Makes the species vulnerable to changing climactic conditions due to the inability to adapt.
What is species diversity? Species richness (number of different species in an ecosystem) Relative abundance (the proportion of each species in an ecosystem)
What is the importance of species diversity? More species in an ecosystem the greater the diversity, therefore more stable community.
What does high species diversity lead to? A stable ecosystem.
What effect does a dominant species have on species diversity? Species diversity is reduced.
What is ecosystem diversity? The variety / number of different ecosystems in a defined area.
A region with a wide variety of ecosystems will have .... species diversity?? Greater / high.
The more remote and isolated an ecosystem is, the species diversity is? Lower.
What effect does a dominant species have within a community? The community has lower species diversity than one with the same species richness but no particularly dominant species.
Many species are comprised of? Several isolated populations.
What is gene flow? The movement of alleles between populations
Gene flow keeps neighbouring populations similar in..? Genotype
What is the result of low gene flow? Increases the chance of populations evolving into different species.
What is a habitat island? A true island (surrounded by water) or an isolated habitat (an oasis in a desert / forest surrounded by roads)
What are the 2 factors of a habitat island? The degree of isolation of the island (the more isolated, the lower the species diversity) The size of the island (larger the island, greater the species diversity)
What is genetic drift? the random changes in allele frequency in a gene pool due to chance
Where does genetic drift have a greater / faster effect? In small populations.
What are the 3 main origins of genetic drift? Founder effect, Population Bottleneck, Neutral mutations.
What is the founder effect? (1) Small population of a new species moves (non random) to a new location away from main population that still exists.
What is the founder effect? (2) By chance alone, gene sequences of founders are disproportionately high in the resulting population compared to original population
What are the effects of the founder effect? Genotype reflects founders. Genes that are rare in original population may become concentrated. The founding of a new population leads to genetic drift.
What is Population bottleneck? a sharp reduction in the size of a population for at least one generation following an event.
What events do population bottlenecks occur after A natural disaster (earthquake) or human activities (over exploitation, overhunting/ predation / disease / climate change)
What does the small population no longer have? The genetic variation to enable evolutionary responses to environment change.
What is the result of a population bottleneck? (1) Event kills off most of the population of the species at random, irrespective of genotype and leaves a handful of survivors.
What is the result of a population bottleneck? (2) Genotype of population reflects the survivors.
What is the consequence of a population bottleneck? (1) It reduces the genetic diversity of a population (due to loss of alleles)
What is the consequence of a population bottleneck? (2) small population numbers can be critical for many species as if the survivors are genetically similar, inbreeding will result in poor reproductive rates.
what are neutral mutations? random changes in DNA sequence that are neither beneficial, nor harmful. They do not effect the ability of an organism to reproduce.
Why does natural selection not act on the neutral mutations? Because they do not confer a survival advantage in an environment. Their frequency in a population is altered by genetic drift.
What happens to the alleles in small populations that are present as a result neutral mutations? Some may drift to high frequency / low frequency / lost over time.
Some species may have a naturally low level of genetic diversity in their population yet remain ...? Viable
What does viable mean? A plant / animal / cell is capable of surviving / living successfully, especially under particular environmental conditions.
What is exploitation? The harvesting of a natural resource (making the best use of a resource to the point where it will recover)
What is overexploitation? Harvesting of a natural resource at a faster rate that it can be replaced
What is an example of over exploitation? Megafauna (Woolly Mammoth, Giant sloth) became extinct due to overhunting by humans.
What can a decrease in overexploitation lead to? a recovery of a population.
What happens when a population of a species becomes extinct locally? Genetic diversity decreases
why can a loss of genetic diversity be critical for many species? Because inbreeding within the remaining population results in poor reproductive rates.
What happens to genetic diversity when a species becomes extinct? Small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change.
What human activities lead to habitat loss? Deforestation, urbanisation.
what is habitat fragmentation? When several areas of habitat become isolated from each other.
What causes habitat fragmentation? road building, agriculture, urbanisation.
What can edges of habitats suffer from? Edge degradation (which may further reduce their size?
How does edge degradation occur? The edges of habitat fragments may be subject to erosion by water and wind, large areas of soil / land are removed.
What increases the rate of a dominant species? A small habitat size
What impact does habitat fragmentation have on species richness? Fragments have limited resources and support lower species richness. Fragments only supporting small populations are more vulnerable to extinction.
What happens to edge length as a result of habitat fragmentation? It increases.
What do edge species do as a result of habitat fragmentation? Colonise the new edge and invade the interior habitat (compete for limited resources at the expense of interior species)
What are habitat corridors? narrow strips of land between habitat fragments.
What do habitat corridors do? Remedy wide spread habitat fragmentation (isolated fragments can be linked with habitat corridors allowing species to move and recolonise habitats after local extinctions (to feed, mate in other areas)
Why do humans introduce non-native species? Pets, biological control, agriculture, aesthetic value.
How can non - native species be introduced accidentally by humans? (animals) Come across on ships bringing food, insects in soil, insects carried on plants
How can non - native species be introduced accidentally by humans? (plants) seeds, spores, viable fragments may be carried on other plants, shoes, vehicles (trains) in soil, clothing, boots
Why was the Japanese Knotweed introduced? As an ornamental plant (intentional)
Why have the Japanese Knotweed become invasive? spreads rapidly in wild by natural means, spread by humans, dont spread seeds.
What impact have Japanese Knotweed had on native species / environment / economy? Outcompetes native flora, contributes to river bank erosion.
Japanese Knotweed impact on biodiversity (genetic, species, ecosystem) It is a dominant species, large abundance, decreases species diversity.
What is climate change? A long term change in global or regional climate patterns or average temperature
What is global warming? A gradual increase in the overall temperature of the earths atmosphere due to green house gases?
What manmade activities have influenced climate change? Burning fossil fuels, industry, agriculture.
What have human activities accelerated? The production of greenhouse gases which leads to increased trapping of heat resulting in manmade global warming.
Why do humans burn fossil fuels? To provide energy for increasing world population (produces CO2)
Why do humans use intensive farming of cattle? To provide meat and dairy products for growing population (produces methane)
What affect do greenhouse gases have normally? warm the surface of the earth by re-radiating heat back to the earths surface.
What affect do greenhouse gases have in excess? They contribute to climate change - these changes are expected to affect biodiversity.
What biotic factors can be used to study climate change? Monitoring - (time of flowering / in spring time) (range of temperature sensitive species) (frequency of temperature induced events - coral bleaching) (movement of species which would affect ecosystem richness)
What abiotic factors can be used to study climate change? temperature, rainfall, wind direction, air population.
Created by: StudyMore6outof7