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Flip to reveal answersWhy do ecologists use sampling?
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All 25 Flashcards — Population interactions
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Question
Why do ecologists use sampling?
Answer
Because counting every individual is usually impossible; sampling estimates population size from a representative subset.
💡 Hint
Estimate from a subset
Question
Define predation.
Answer
Predation is an interaction where a predator hunts, kills and eats a prey organism.
💡 Hint
Predator eats prey
Question
Quick check: Carrying capacity means what?
Answer
The maximum population size the environment can support sustainably over time.
💡 Hint
Max sustainable size
Question
Name the four processes that change population size.
Answer
Births, deaths, immigration and emigration.
💡 Hint
BDIE
Question
Define carrying capacity (K).
Answer
Carrying capacity is the maximum population size an environment can support sustainably over time.
💡 Hint
Max sustainable size
Question
When is a quadrat used?
Answer
Quadrats are used to sample non-mobile organisms (mainly plants) to estimate density, frequency or percentage cover.
💡 Hint
Non-mobile organisms
Question
Define limiting factor.
Answer
A limiting factor is an environmental factor that restricts population growth, size or distribution.
💡 Hint
Acts like a brake
Question
In predator–prey cycles, which population peaks first?
Answer
The prey population peaks first; the predator peak usually lags behind.
💡 Hint
Prey first
Question
Quick check: Which peaks first in predator–prey cycles?
Answer
Prey peaks first; predator peaks later due to time lag.
💡 Hint
Prey first
Question
Define competition.
Answer
Competition is the demand by two or more organisms for the same limited resource.
💡 Hint
Limited resource
Question
What does Liebig’s Law state?
Answer
Population growth is limited by the factor in shortest supply, even if other resources are abundant.
💡 Hint
Lowest bar sets limit
Question
What is the difference between mutualism and parasitism?
Answer
Mutualism benefits both species; parasitism benefits the parasite while harming the host.
💡 Hint
Both benefit vs one harmed
Question
Define negative feedback in population control.
Answer
Negative feedback is a process that reduces change and returns a population towards balance (for example predators increase when prey increase).
💡 Hint
Thermostat idea
Question
What is a transect used for?
Answer
A transect is used to show how species or abundance change across an environmental gradient (for example shore to land).
💡 Hint
Change across gradient
Question
Quick check: Name the “lowest bar sets the limit” idea.
Answer
Liebig’s Law of the minimum.
💡 Hint
Lowest bar
Question
Quick check: Quadrat is best for what organisms?
Answer
Non-mobile organisms, mainly plants (and very slow animals).
💡 Hint
Plants
Question
Why is disease often density-dependent?
Answer
Pathogens spread faster when population density is high because individuals contact each other more often.
💡 Hint
Crowding increases spread
Question
Write the Lincoln Index for capture–mark–recapture.
Answer
N = (n1 × n2) / m, where n1 is marked first, n2 is caught second, and m is recaptured marked.
💡 Hint
N equals n1 times n2 over m
Question
Give one density-dependent and one density-independent factor.
Answer
Density-dependent: competition, disease, predation. Density-independent: drought, flood, fire, storm.
💡 Hint
Depends on density vs not
Question
What is a time lag in population dynamics?
Answer
A time lag is a delay between a change in one population and the response of another population.
💡 Hint
Delay in response
Question
Exam cue: In a bar chart of limiting factors, what do you identify?
Answer
Identify the lowest bar and state it is the limiting factor because it caps population size.
💡 Hint
Lowest bar
Question
Name one key assumption of capture–mark–recapture.
Answer
The population is closed (no immigration/emigration) and marks are not lost and do not affect survival or capture.
💡 Hint
Closed population
Question
Exam cue: When asked “describe an interaction”, what must you state for marks?
Answer
Name the interaction and state who benefits and who is harmed (or how resources are affected).
💡 Hint
Who benefits / harmed
Question
Quick check: Write the Lincoln Index.
Answer
N = (n1 × n2) / m.
💡 Hint
N equals n1 times n2 over m
Question
Exam cue: In data questions about cycles, what should you do first?
Answer
Describe the pattern (rise, fall, oscillation, time lag) before explaining the cause.
💡 Hint
Describe then explain
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Full study notes for Population interactions
Topic 2.3 hub
Habitat, niche and interactions
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