13. Ecological Techniques Flashcards

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1
Q

What is Ecology

A

the scientific study of the factors which determine the distribution and abundance of organisms

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2
Q

What is an ecosystem

A

the environment and all the organisms that live in an area.

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3
Q

How do you investigate ecosystems

A

look at the abundance of organisms in a particular area or their distribution throughout.

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4
Q

How can ecosystems be studied

A

-Randomly placed quadrats or quadrats along a belt transect for slow moving organims
-Mark-release recapture method

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5
Q

Why is random sampling used

A

· avoid bias
· be representative
· produce statistically significant results

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6
Q

How are random coordinates generated

A

Random number table, calculator or computer

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7
Q

How big should a random sample be

A

Sample 20 quadrats and record the abundance of organisms in each quadrat. Big enough to
· to be representative of the population
· to allow a statistical test to be carried out on the data.

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8
Q

What are the different ways to measure abundance when using a quadrat

A

-Measuring frequency of a species - record the presence or absence
-Measures of percentage cover - Proportion of the ground occupied
-Measures of species diversity- counting the number of individuals of a species

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9
Q

What is the advantage and disadvanatges of measuring frequency of a species

A

AD- Quick and easy in large scale ecosystems
DISAD - Results are not detailed as one organism in a species counts the same as 100 in a different quadrat

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10
Q

What are advatnages and disadvanatges of measures of percentage covers

A

AD - Quick
DISAD - it is a little subjective, so estimates by different workers will vary.

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11
Q

What is the advantage and disadvanatges of measures of species density

A

AD - Allows you to calculate an estimate of the population size. Can calculate species diversity.
DISAD - Time consuming. Must be able to distinguish one organism from another.

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12
Q

How do you estimate the total population size

A

need to know the mean number of organisms in a quadrat and the area of the ecosystem being sampled.

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13
Q

How do you investigate distribution

A

If you are trying to find out how species distribution changes across an area you need to sample systematically
-From lake to shore
-Up rocky shore from sea to land
Can use
-A line transect
-Belt transect

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14
Q

What is a line transect

A

measuring tape stretched across the habitat and plants are sampled at regular intervals
Each plant touching the line is identified and recorded.
Quick and provides a non-quantitative idea of some of the more typical species present.
Useful in illustrating the main features of a zonation such as a succession from a water community to a land one.

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15
Q

What is a belt tansect

A

This gives a more detailed record of the changes.
Quadrats placed next to each other along a transect and estimates of the percentage cover or frequency of each species is recorded.

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16
Q

How do you measure abundance in mobile animals

A

Random sampling or systematic sampling can still be used but there needs to be a method to capture the organism first.
Mark-release-recapture

17
Q

Waht is the mark-release recapture method

A

· A large sample of the organisms needs to be collected
· They are then marked, counted and released back into population and allowed time to remix with the rest of population.
· method of marking must not harm animal or affect their survival chances.
· After release, give animals enough time to get thoroughly mixed in with the rest of the population
· Then capture a large sample, using the same sampling technique. Count total number which you catch, and the number of these which are marked.

18
Q

How can you calculate the population size from the M-R-R method

A

Lincon Index:

Pop estimate = (#Captured and marked 1st x Total # 2nd time) / # recaptured

19
Q

Waht assumptions are made about the organisms when using M-R-R

A

· no immigration or emigration
· no births or deaths
· marking does not affect likelihood of being recaptured or preyed upon
· marked individuals have had chance to mix fully back into population