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Biology > Unit 4: Population > Flashcards

Unit 4: Population Flashcards

1
Q

How would place the quadrats at random

A

1) Split area into squares using TAPE MEASURE
2) Assign coordinates to each square
3) Find coordinates on a grid
4) BY generating random numbers: from a CALCULATOR 📲

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2
Q

Why is it important to check the REPEATABILITY of the measurements

A
  • Increases the reliability of measurements

* If measurements are repeatable, differences LESS LIKELY to be due to measurement/anomalies unlikely

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3
Q

Explain what is meant by “POPULATION”

A

All organisms of 1⃣ species in a HABITAT at 1⃣ time

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4
Q

Two reasons why people might be living longer…having less children?

A
  • Contraception
  • More medical/health care
  • Food 🍖 availability
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5
Q

What info is needed to calculate the GROWTH RATE of a POPULATION?

A

Birth 👶 RATE + Death 👼 RATE

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6
Q

3 factors that lead to a DECREASE in the DEATH RATE 😪

A
  • Improved medical care
  • More food 🍕
  • War ends
  • Lower Infant Mortality
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7
Q

What’s meant by “COMMUNITY”

A

ALL the organisms
present 🎁
In an area

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8
Q

Describe the MARK-RELEASE-RECAPTURE method:

A

1) CAPTURE sample, MARK & RELEASE
2) HarmLESS 🙅 method of marking e.g. Paint 🎨
3) Take second sample and count MARKED organisms
4) EQUATION

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9
Q

What’s the equation for Mark-Release-Recapture?

A

Population = No. in x No. in
sample 1 sample 2
___________________________________

Number MARKED 🎨 in Sample 2⃣

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10
Q

Why collect data from a LARGE number of specimens, at RANDOM?

A
  • Results more REPRESENTATIVE/RELIABLE
  • ANOMALIES LESS SIGNIFICANT
  • Random overcomes BIAS
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11
Q

Advantages of collecting QUANtitative data about plant distribution as PERCENTAGE COVER?

A
  • Data collected RAPIDLY

* Does not require DEFINING INDIVIDUAL PLANTS

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12
Q

Define “ECOSYSTEM”

A

all BIOTIC 🏃 and ABIOTIC 🚲 factors of an AREA

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13
Q

Suggest how the introduction of (Grey Squirrels) led to a REDUCTION in the diversity of the community?

A
  • Competes for food/nutrients
  • Some of original SPECIES lost
  • Loss of NICHES
  • Consumers DIE or some MIGRATE
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14
Q

Name some BIOTIC factors:

A
  • Food
  • Disease
  • Predators
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15
Q

Name some ABIOTIC factors:

A
  • Light
  • Humidity
  • pH
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16
Q

How might DEFORESTATION cause a reduction in species population…

A

• Deforestation involves DESTRUCTION of NICHES:

  • Some PREY animals MOVE OUT/DIE
  • Less FOOD for species
17
Q

Why is the length of the food chain longer?

A

MORE ENERGY initially at the START of the (longer) food chain. So, more energy AVAILABLE for NEXT STAGES 💤

18
Q

Define “BIRTH RATE”

A

births per 1000

PER YEAR

19
Q

How do you decide the number of quadrats to use?

A
  • enough to carry out a STATISTICAL test
  • a large number to make sure results are RELIABLE
  • need to ensure work can be carried out in the TIME available
20
Q

How can you investigate the PERCENTAGE COVER of daffodils in the field? (5 marks)

A
  • use QUADRATS to measure PERCENTAGE COVER of daffodils
  • SEVERAL placed on ground at RANDOM LOCATIONS within field
  • the PERCENTAGE of each QUADRAT is recorded
  • the PERCENTAGE COVER could be ESTIMATED by AVERAGING the data collected in all the quadrats
21
Q

In a predator-prey relationship, the predator levels have significantly dropped yet prey levels have began DROPPING, why?

A

due to INTRAspecific competition

22
Q

What does the Demographic Transition Model show? (5 points)

A

it shows CHANGES in BIRTH RATE 👶 and DEATH RATE 👵 and TOTAL POPULATION SIZE for a HUMAN population over a LONG PERIOD of TIME ⏰

23
Q

What happens in Stage 1 of the Demographic Transition Model: (2 points then EXPLAIN why?)

A
  • Birth and Death rates fluctuate at high level
  • Population size is low and NOT increasing

Birth rate ⬆️ cos no birth control or family planning and education is poor
Death rate ⬆️ cos poor health care, poor sanitation and diet

24
Q

What happens in Stage 5 of Demographic Transition Model? (3 points then 2 EXPLAIN why?)

A
  • Birth rate begins to FALL
  • Death rate remains STABLE
  • Population is HIGH but SHRINKING
  • Birth rate ⬇️ children are expensive and people have dependant elderly relatives
  • Death rate remains steady as larger populations of elderly people die
25
Q

Explain what happens in Stage 2 of the Demographic Transition Model: (3 points then 2 EXPLAIN)

A
  • Birth rate remains HIGH
  • Death rate FALLS ⬇️
  • Population size INCREASES rapidly
  • Birth rate remains high cos little birth control 🚫 or family planning 👪
  • Death rate falls cos of better health care, sanitation and diet
26
Q

Describe what happens in Stage 4 of the Demographic Transition Model: (2 points then 1 EXPLAIN)

A
  • Birth rate and Death rate FLUCTUATE 📈 at a LOW level
  • Population remains STABLE but HIGH

• Birth rate stays low bc increased demand for luxuries so less $$ available to raise children 👫

27
Q

Describe what happens in Stage 3 of the Demographic Transition Model: (3 points then 1 EXPLAIN)

A
  • Birth rate FALLS ⬇️ RAPIDLY
  • Death rate FALLS more SLOWLY
  • Population INCREASES at a SLOWER rate

• Birth rate ⬇️ bc INCREASED use of birth control 🚫 and family planning 👪

28
Q

Describe “Succession”: (6 marks)

A
  1. Colonisation by pioneer (plant) species
  2. Change in environment e.g. add humus/nutrients
  3. Makes a LESS HOSTILE habitat
  4. Enables other species to colonise
  5. They OUTCOMPETE pioneer species and become the new DOMINANT species
  6. Change in BIODIVERSITY
  7. Climax community (final SERAL STAGE)
29
Q

How can you investigate the AMOUNT of a POPULATION in a field? (4 marks)

A
  • Use appropriate technique to sample e.g. quadrats/pitfall traps/pooters to TAKE SAMPLE OF THE POPULATION
  • Samples should be RANDOM
  • Repeat i.e. take as many tamples as possible
  • take the average of the DATA COLLECTED and MULTIPLY it by the SIZE of the whole area

Biology (14 decks)

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