Flashcards
AQA A2 Biology Unit 4: Populations
Cards in this deck (40)
- 1what is the difference between biotic and abiotic factors?abiotic factors of the non living component ecosystem, whilst biotic factors are the living components of an ecosystem
- 2name two things that must be considered within an ecosystemthe flow of energy through the system and the cycling of elements within the system
- 3define populationa group of interbreeding organisms of one species in a habitat
- 4Define communityall the populations of different organisms living and interacting in a given place at the same time
- 5define habitatthe place where a community of organisms live, within an ecosystem there are many habitats
- 6what is an ecosystem made up of?all of the interacting biotin and abiotic features in a specific area
- 7what is a nichedescribes how an organism fits into the environment, where are organisms lives and what it doesdoes. no two organisms occupy the same niche
- 8why is random sampling usedto avoid bias when collecting data
- 9describe the process of random samplinglayout to two tape measures at right angles octane coordinates using random numbers and place the quadrat at the intersection of the coordinates
- 10name three factors to consider when using quadratsthe size of the quadrat, depends on size of organism and how it is distributed. number of quadrats to use, generally the greater number the better. the position of the contract within the area, random sampling or systematic sampling
- 11when would systematic sampling be appropriate to usewhen a transition is taking place
- 12how would you carry out systematic samplinglayout a straight line of string stretched over the area, either place quadrats along the string or record all organisms touching the string
- 13define abundancenumber of individuals of a species within a given space
- 14describe two methods of measuring abundancefrequency, the likelihood of a species occurring in a quadratic. percentage cover, an estimate of the area within a quadrat that a plant species covers
- 15when and how is mark release recapture be usedis useful when investigating animal species. first a known number of animals are caught marked and released back into the community later organisms are recaptured and the number of marks recorded this information is used to estimate the population size
- 16what equation is used to estimate population size using mark release recapture datapopulation size equals (number in first sample x number in second samplesample) divided buy number of marked re captured x 100
- 17describe for the simpsons that must be made when using mark release recapture estimate population sizeno migration or immigration, no birth or deaths, doesn't increase chance of predation, proportion of marked to unmarked individuals in the second sample is representative of the population, marked individualsindividuals distribute themselves evenly throughout the population
- 18describe the three general periods Found on a population growth curvea period of slow growth, as the initially small number of individuals reproduce slowly. a period of rapid growth, where the growing number of individuals continue to reproduce. a period of decline until a more or less stabel number is achieved with cyclic fluctuations
- 19name and explain for a biotic limiting factorstemperature, each species has an optimum temperature for enzyme activity.
light intensity determines the rate of photosynthesis, ph affects enzyme action, water and humidity affect transpiration and photosynthesis - 20when and why does competition occurTwo or more individuals share resources are insufficient to satisfy all their requirements
- 21what is intraspecific competitioncompetition between individuals of the same species for resources such as food and water, the availability of such resources determines the population
- 22What is interspecific competitioncompetition between individuals of different species
- 23what is the competitive exclusion principlewhere populations of two species occupy the same niche one will have a competitive advantage over the other, this population will increase over time whilst the other will diminish
- 24what is a predatoran organism which feeds on other organisms known as their prey
- 25how have predators and prey evolvedPredators have evolved to become better at catching prey whilst prey evolve to become better at a avoiding predators
- 26summarise how are predators prey relationships or cyclic fluctuation in population sizepredators eat pray reducing prey population. Fewer prey so more intraspecific competition. Predator population reduced. Fewer predators so fewer prey eaten. Prey population increases. More prey available to eat so predator population increases.
- 27How are population crashes advantageous to organisms?Important in evolution, as create a selection pressure, individuals which survive are better adapted to prevailing conditions.
- 28How has human population size changed over time?Started very small, with large amount s of disease and famine causing regular crashes thus keeping population fairly constant. Population slowly increases however disease kept it fairly low. Population increases exponentially due to improved medicine, sanitation and food availability.
- 29What two basic factors affect population growth?Birth and death rates
- 30Distinguish between emigration and immigrationImmigration is when individuals join a population
Emigration is when individuals leave a population - 31Equation for population growth(Births + immigration) - (Deaths + emigration)
- 32Equation for percentage population growth rate(Population growth during period) ÷ (population at the start of the period) × 100
- 33Factors affecting birth rateEconomic conditions
Cultural and religious background
Social pressures and conditions
Birth control
Political factors - 34Equation for birth rate(Number of births in a year) ÷ (total population in the same year) × 100
- 35Factors affecting death rateAge profile
Life expectancy at birth
Food availability
Safe drinking water availability
Sanitation
Medical care
Natural disasters
War - 36Equation for death rate(Number of deaths per year) ÷ (total population in the same year) × 100
- 37Describe the shape of a stable population pyramid, and say what causes itWidth of boxes gradually decreases towards the top. Caused by birth and death rates being in balance not no net increase or deacrease in population size.
- 38Describe the shape of, and what causes an increasing population pyramidBottom of pyramid much wider, decreases steeply to a lower maximum age. Caused by a high birth rate and few elderly people.
- 39What does an decreasing population pyramid look like, and what causes it to occur.Steady width much of the way up, higher maximum. Caused by low birth and mortality rate.
- 40What is average life expectancy?Age at which half of the population is still alive
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- Question cards relating to AQA A2 Biology Unit 4 Topic 1: Populations
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