3.7.4 Populations in ecosystems Flashcards
What is a community in ecology
A community is all the populations of different species living and interacting in the same habitat at the same time
What is an ecosystem
An ecosystem is a community and the non-living abiotic factors in an area interacting as a system
What determines the niche of a species
A species’ niche is determined by its adaptations to abiotic and biotic factors
What is carrying capacity
Carrying capacity is the maximum stable population size that an ecosystem can support over time
What abiotic factors affect population size
Abiotic factors affecting population size include temperature light water availability oxygen levels and soil pH
What is interspecific competition
Interspecific competition is competition between individuals of different species for the same resources which can affect population sizes
What is intraspecific competition
Intraspecific competition is competition between individuals of the same species for resources affecting survival and reproduction
What is predation
Predation is when one organism (the predator) kills and consumes another organism (the prey) affecting population sizes
How can population size of slow-moving organisms be estimated
Population size of slow-moving organisms can be estimated using randomly placed quadrats or quadrats along a belt transect
What method is used to estimate population size of motile organisms
The mark-release-recapture method is used to estimate population size of motile organisms
What assumptions are made in mark-release-recapture
No births deaths immigration or emigration marked individuals mix randomly with population marking does not affect survival or predation all marks are still visible
Why are ecosystems considered dynamic
Ecosystems are dynamic because abiotic and biotic factors constantly change influencing population sizes and community structure
What is primary succession
Primary succession is the process by which a barren area is colonised by pioneer species leading to a climax community
What role do pioneer species play in succession
Pioneer species modify the abiotic environment making it more suitable for other species by adding organic matter improving soil structure and increasing nutrient availability
How can new species affect the environment in succession
New species may change the environment to be more suitable for other species with different adaptations but less suitable for previous species
How can changes in abiotic factors affect biodiversity
Changes in abiotic factors can create a less hostile environment increasing biodiversity by allowing more species to survive
Why does conservation often involve managing succession
Managing succession prevents climax communities from forming maintaining habitats for certain species and preserving biodiversity
Why is there a conflict between human needs and conservation
Humans need land resources and economic development which can conflict with conservation efforts to maintain biodiversity and ecosystem stability
How can sustainability be achieved in conservation
Sustainability is achieved by balancing resource use with conservation efforts ensuring ecosystems and biodiversity are maintained for future generations
What calculation is used in mark-release-recapture
Estimated population size = (number of marked individuals in first sample × total number in second sample) / number of marked individuals recaptured
Mark, Release, Recapture – Assumptions (5)
- No emigration/immigration;
- No losses to predation;
- Marking does not affect survival;
- Birth rate and death rate equal;
- (In this case) all belong to one population;
Mark, Release, Recapture – Outline the method (4)
1. Capture/collect sample, mark and release;
2. Ensure marking is not harmful (to fish)
OR
Ensure marking does not affect survival (of fish);
3. Allow (time for) fish to (randomly) distribute before collecting a second sample;
4. (Population =) number in first sample × number in second sample divided by number of marked fish in second sample/number recaptured;
Describe how you could estimate the size of a population using random sampling (4)
- Use a grid OR Divide area into squares/sections;
- Method of obtaining random coordinates/numbers e.g. calculator/computer/random numbers table/generator;
- Count number/frequency in a quadrat/section; .
- Large sample and calculate mean/average number (per quadrat/section);
- Valid method of calculating total number of plant,
e.g. mean number of plants per quadrat/section/m2 multiplied by number of quadrats/sections/m2 in area
Why repeat/ large sample size
So /representative;
The scientist used percentage cover rather than frequency to record the abundance of algae present.
Suggest why. (1)
too many to accurately count / individual organisms not identifiable / too small to identify / overlap;
Describe use of systematic sample to count plants (5)
- Systemic sampling (placing quadrat) at regular intervals along transect line;
- Transect line from/to ……..;
- Count number/frequency in a quadrat/section;
- Large sample and calculate mean/average number (per quadrat/section);
Effect of increased plant/animal diversity on ecosystem (3)
- Increase in plant diversity leads to more different types of food for animals;
- Increase in variety of animals leads to increase in predator species;
- Increase in more different niche/habitat;
Define niche (3)
- Niche is the role that a species plays in within a community;
- Includes food resources;
- No two species can occupy identical niche;
Predator-Prey Relationship (4)
- As pest numbers increase more food or predators, so they increase;
- Increased predation of pests reduces numbers;
- Low number of pests results in less food for predators, so their numbers decrease;
- Low predator numbers allow pest population to rise as fewer are eaten;
Succession (5)
- (Colonisation by) pioneer species;
- Pioneers/species/organisms change the environment/habitat/conditions/factors;
- (Environment becomes) less hostile for other/new species Accept previous species out-competed.
- increase in diversity/biodiversity;
- (To) climax community;
Succession – Competition (3)
- Pioneer species increases then decreases;
- Principle of a species changing the conditions / a species makes the conditions;
- New/named species better competitor / pioneer species outcompeted;
Give two features of a climax community.
1. Same species present (over long time) / stable community (over long time);
2. Abiotic factors (more or less) constant (over time)
3. Populations stable (around carrying capacity)
Suggest one reason for conserving woodlands. (1)
- Conserving / protecting habitats / niches;
- Conserving / protecting (endangered) species / maintains / increases (bio) diversity;
- Reduces global warming / greenhouse effect / climate change / remove / take up carbon dioxide;
- Source of medicines / chemicals / wood;
- Reduces erosion / eutrophication.
Lake Malawi in East Africa has more species of fish than any other lake in
the world.
Suggest and explain how this speciation may have occurred.
- Variation/differences due to mutation/s;
- (Reference to) allopatric (speciation);
Ignore sympatric speciation. - Smaller/different lakes have different environmental conditions
OR
Smaller/different lakes have different selection pressures;
Accept different populations for different lakes. - Reproductive separation/isolation
Suggest why the mark-release-recapture method can produce unreliable
results in very large lakes
Less chance of recapturing fish
OR
Unlikely fish distribute randomly/evenly;
