Biology Edexcel A Level (Topic 4) Test and Verified Answers

4.1: Explain how the variety of species has generally increased over time. - Variety of life has become more extensive because species adapted to all environments in the world- even extreme habitats. 4.2: Explain the negative impact that some human activities (give 3 examples) have on diversity of species. - -Deforestation/loss of habitat leads to decrease in species richness -Whole ecosystems are affected when species rapidly decline -Leading to extinction or imbalance in a habitat (deforestation, pollution, ozone damage) 4.3: Define the following terms and give a named example of each: species, community, population, habitat, niche, environment, inter-specific completion, intra-specific competition. - -Species: group of organisms which produce fertile offspring, and are reproductively isolated from other species, e.g.: Great Panda -Community: all the living organisms present in an area, e.g.: squirrels, birds, worms, etc. In a forest -Population: a group of interbreeding individuals belonging to one species -Habitat: particular place where a community is found with specific conditions -Niche: the role an organism plays in its environment (how it lives/fits in) -Environment: external surroundings (biotic and abiotic) -Inter-specific Competition: between different species -Intra-specific Competition: between the same species 4.4: Explain what is meant by the term "behavioral adaptations" to the environment, and give an example. - Any actions by an organism that help them to survive or reproduce, e.g.: grey squirrels bury acorns to act as larders in times of food shortages. 4.5: Explain what is meant by the term "physiological adaptations" to the environment, and give an example. - Features of the internal workings of organisms which help them to survive or reproduce, e.g.: some bacteria have very thermo-stable enzymes so they can tolerate conditions in hot springs of up to 80C and deep sea vents of up to 350C. 4.6: Explain what is meant by the term "anatomical adaptations" to the environment, and give an example. - Structures we can see when we observe or dissect an organism, e.g.: camouflage on tigers (stripes) 4.7: Explain how the concept of niche accounts for distribution and abundance or organisms in a habitat. - No two animals can be successful in the same niche, therefore most animals adapt so they have their own niche or one with very little overlap. In a habitat, this will cause the distribution of organisms to be more spread out and the abundance of competing organisms to decrease. 4.8: Define the terms "natural selection" and "evolution." - Natural Selection: the mechanism by which organisms change over time as they adapt to their changing environments. Evolution: a change in allele frequency in a population over time/generations. 4.9: Explain what is meant by "survival of the fittest" and give an example. - The winners in the struggle for existence are those that possess some characteristics which are advantageous/beneficial; this differential survival is known as "survival of the fittest".