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Unit 3 Biology
Booklet 2
Question | Answer |
---|---|
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. |