3.7.4 Populations in ecosystems Flashcards
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 in experiments
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)
what is the 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;
describe 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 – describe 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;
2. Conserving / protecting (endangered) species / maintains / increases (bio) diversity; - Reduces global warming / greenhouse effect / climate change / remove / take up carbon dioxide;
- Source of medicines / chemicals /