Populations in ecosystems Flashcards

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1
Q

Define ecology.

A

The study of inter-relationships between organisms and their environment including abiotic and biotic.

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2
Q

Define populations.

A

A group of individuals of one species that occupy the same habitat at the same time.

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3
Q

What factors affect the size of a population?

A
  • the effect of abiotic factors
  • interactions between organisms of different species form a community
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4
Q

Define a community.

A

Populations of different species living and interacting in a particular place at a specific time.

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5
Q

Define a species.

A

A group of organisms that can interbreed to produce fertile offspring.

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6
Q

What is an ecological niche?

A

Describes how organisms fit into an environment, governed by its abiotic and biotic adaptations.

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7
Q

Define population size.

A

The number of individuals in a population.

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8
Q

Describe abiotic factors influencing population size.

A
  • Temperature: temperature falls below optimum meaning enzymes work slower and denature.
  • Light: ultimate energy source for most ecosystems.
  • pH: affects enzyme activities.
  • Water and humidity: affect transpiration rates, where water is scarce and populations are small.
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9
Q

Define immigration.

A

Where individuals join a population from outside.

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10
Q

Define emigration.

A

Where individuals leave a population.

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11
Q

Define competition.

A

Where 2 or more individuals share any resource that’s insufficient to satisfy all their requirements fully, competition results.

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12
Q

Describe intraspecific competition.

A
  • Competition between members of the same species for resources.
  • Greater availability of resources allows for a greater population, and vice versa.
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13
Q

Describe interspecific competition.

A
  • Individuals of a different species compete for resources.
  • When 2 species compete, one usually has a competitive advantage, one population gradually increases and the other diminishes.
  • When one species fully dies, it is known as the competitive exclusion principle.
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14
Q

Define the competitive exclusion principle.

A

When two species compete, the one that uses the resources most effectively eliminates the other. No two species can occupy the same niche.

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15
Q

Define predation.

A

Occurs when an organism is consumed by another.

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16
Q

Describe the effect of predator-prey relationships on population size.

A
  • Predators eat their prey, reducing prey population.
  • Fewer prey means competition between predators increases.
  • Predator populations reduce as some are no longer able to survive and reproduce.
  • Fewer predators means prey can reproduce so their populations increase.
  • Which in turn, increases predator population.
17
Q

Define abundance.

A

The number of individuals of a species in a given space.

18
Q

Name two sampling techniques to study habitats.

A
  • random sampling (frame quadrats)
  • systematic sampling (transect belt)
19
Q

Describe point quadrats and frame quadrats.

A
  • Point quadrats (horizontal bar supported by two legs) - consists of ten holes; throughout each a pin is dropped. Every species that touches the pin is recorded.
  • Frame quadrats (square frame divided by string of wire into equally sized subdivisions) - quadrat placed in different locations within the area. The abundance of quadrat is recorded.
20
Q

Describe sampling at random.

A
  1. Lay out two long tape measures at right angles, along two sides of the study area.
  2. Obtain a series of coordinates by using random number taken from a table or generate by a computer.
  3. Place a quadrat at the intersection of each pair of coordinates and record the species within it.
21
Q

Describe variations due to genetic factors.

A
  • Mutation: chromosomes may or may not be changed and passed onto the next generation.
  • Meiosis: special form of nuclear division that produces new combinations of alleles before they are passed into the gametes, all of which are therefore different.