3.7.4 Populations in ecosystems Flashcards

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1
Q

Mark, Release, Recapture – Assumptions (5)

A
  1. No emigration/immigration;
  2. No losses to predation;
  3. Marking does not affect survival;
  4. Birth rate and death rate equal;
  5. (In this case) all belong to one population;
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2
Q

Mark, Release, Recapture – Outline the method (4)

A

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;

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3
Q

Describe how you could estimate the size of a population using random sampling (4)

A
  1.  Use a grid OR Divide area into squares/sections;
  2.  Method of obtaining random coordinates/numbers e.g. calculator/computer/random numbers table/generator;
  3.  Count number/frequency in a quadrat/section; .
  4.  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;
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4
Q

Why repeat/ large sample size in experiments

A

So /representative;

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5
Q

 The scientist used percentage cover rather than frequency to record the abundance of algae present. Suggest why. (1)

A

too many to accurately count / individual organisms not identifiable / too small to identify / overlap;

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6
Q

Describe use of systematic sample to count plants (5)

A
  1. Systemic sampling (placing quadrat) at regular intervals along transect line;
  2. Transect line from/to ……..;
  3. Count number/frequency in a quadrat/section;
  4.  Large sample and calculate mean/average number (per quadrat/section)
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7
Q

what is the Effect of increased plant/animal diversity on ecosystem (3)

A
  1. Increase in plant diversity leads to more different types of food for animals;
  2. Increase in variety of animals leads to increase in predator species;
  3. Increase in more different niche/habitat;
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8
Q

Define niche (3)

A
  1. Niche is the role that a species plays in within a community;
  2. Includes food resources;
  3. No two species can occupy identical niche;
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9
Q

Predator-Prey Relationship (4)

A
  1. As pest numbers increase more food or predators, so they increase;
  2. Increased predation of pests reduces numbers;
  3. Low number of pests results in less food for predators, so their numbers decrease;
  4. Low predator numbers allow pest population to rise as fewer are eaten;
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10
Q

describe Succession (5)

A
  1.  (Colonisation by) pioneer species;
  2.  Pioneers/species/organisms change the environment/habitat/conditions/factors;
  3.  (Environment becomes) less hostile for other/new species Accept previous species out competed.
  4.   increase in diversity/biodiversity;
  5.  (To) climax community;
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11
Q

Succession – describe Competition (3)

A
  1. Pioneer species increases then decreases;
  2. Principle of a species changing the conditions / a species makes the conditions;
  3. New/named species better competitor / pioneer species outcompeted;
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12
Q

Give two features of a climax community

A

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)

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13
Q

Suggest one reason for conserving
woodlands. (1)

A
  1. Conserving / protecting habitats / niches;
    2.  Conserving / protecting (endangered) species / maintains / increases (bio) diversity;
  2. Reduces global warming / greenhouse effect / climate change / remove / take up carbon dioxide;
  3.   Source of medicines / chemicals /
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