Download Population

Unit 4 revision lesson
Population
Revision objectives
• To go over Populations, Energy and Inheritance.
• Everyone must be familiar with the content and
describe what is required from them using the
specification.
• Most people should confidently answer short
questions and aim for full marks.
• Some people should answer the long exam
questions confidently and aim to get full marks
The specification
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The next few slides show the specification.
I have highlighted all the key words.
I want you to make 3 columns.
Confident to answer questions on this.
Semi- confident.
I pray this won’t come up.
Write each of the keywords in each of the
columns.
The spec
3.4.1 The dynamic equilibrium of populations is
affected by a number of factors.
• A population is all the organisms of one species
in a habitat. Populations of different species form
a community.
• Within a habitat a species occupies a niche
governed by adaptation to both biotic and
abiotic conditions.
• Keywords and definitions.
Investigating populations
• A critical appreciation of some of the ways in which
the numbers and distribution of organisms may be
investigated.
• Random sampling with quadrats and counting along
transects to obtain quantitative data.
• The use of percentage cover and frequency as
measures of abundance.
• The use of mark–release–recapture for more mobile
species.
Investigating populations 2
• In the context of investigating populations,
candidates should
• carry out experimental and investigative activities,
including appropriate risk management
• consider ethical issues arising when carrying out
fieldwork, particularly those relating to the
organisms involved and their environment
• analyse and interpret data relating to the
distribution of organisms, recognising correlations
and causal relationships
• appreciate the tentative nature of conclusions that
may be drawn from such data.
Variation in
population size
• Population size may vary as a result of the
effect of abiotic factors
• interactions between organisms: interspecific
and intraspecific competition and predation.
Human populations
• Population size and structure, population growth
rate, age population pyramids, survival rates and life
expectancy.
• Candidates should be able to
• interpret growth curves, survival curves and age
pyramids
• calculate population growth rates from data on birth
rate and death rate.
• relate changes in the size and structure of human
populations to different stages in demographic
transition.
In relation to exam questions
• Lets look at some past papers!
Population
• Lots of 2 mark questions looking at the
definitions of the key terms.
• Look out for graph questions on predator prey
relationships and competition.
• Be ready to analyses graphs and relate your
knowledge to the situation presented for the
longer data questions.
C
D
E
A
B
With reference to the drawing, explain the meaning of
the terms
(i)
community;
.........................................................................................................
(ii)
population.
...........................................................................................................................(3)
(a)
(b)
Describe how you could use point quadrats to investigate the
distribution of plants at the edge of a pond. (3)
1.(a)(i)All
organisms living in a particular place;
(ii)
All the organisms of one particular species;
Both examples illustrated with reference to drawing;
3
(b) Transect from water onto bank;
Point quadrat frame placed at regular intervals;
Record species touching points;
Calculate percentage/process with kite diagram/
use statistical test to show..;
max 3
Investigating populations
• A mixture of marks and data related questions.
• Can range from 6-15 mark questions.
• Sampling techniques will most likely feature in
the question.
• Make sure that you can describe the different
sampling techniques.
• These questions are most likely to test your
analytical skills so get ready to draw a
conclusion.
• Explain how a frame quadrat is used to find
percentage cover of a species of plant in a
habitat. (3)
• Ground beetles are large black insects. The markrelease-recapture method can be used to
estimate the ground beetle population on a
roundabout. Describe how. (5)
• Describe the techniques you would use to obtain
reliable data in order to compare the sizes of the
populations of the snail in the muddy area and in
the area covered by vegetation. (3)
• Describe one way in which you could place the
quadrats randomly in a field. (2)
Answer
(a)suitable number of quadrats used;
(many/ large number/ 10 minimum)
count all the squares occupied (by the leaves of) one
species; reference to randomising;
description of a method of randomising any 3
b) 1Sample of ground beetles captured and counted (a);
• 2 Released and second sample captured;
• 3 Count total number of beetles (B) and number marked
(b);
• 4 Total population (A) estimated from the relationship ;
• 5 Detail of method e.g. pitfall trap/marking with tippex;
• 6 Refinement to ensure greater accuracy e.g. large
number/ marking in position such that does not affect
survival; 5 max
c)use of large numbers of quadrats in each area (if
number stated then 10+);
random sampling method (e.g. grid + random
numbers)/systematic sampling method (allow
regular sampling along a transect); counting.
OR
(allow capture/recapture method mark and
release; recapture; calculate proportion of
marked snails in second sample)
3
D) Use of grids/coordinates;
Table of random numbers;
2
Human populations
• Will most likely get a 6/7 mark question.
• Population demographic changes are common
questions.
• Expect you to make suggestions to what is
causing change in population.
• Graph interpretation questions are almost
certain.
• Make sure that you can calculate population
change.
Ok lets relate to exam questions
50
Rate per
1000
40
birth rate
30
20
10
death rate
0
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1986
Mauritius is an island in the
Indian Ocean. The graph
shows the birth rate and the
death rate for its human
population between 1890 and
1986.
Total
population
Population
in 1890
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1986
Year
(ii) You would need to know the birth rate and the death
rate in order to calculate the population growth in a
particular year. What other information would you
need? (1)
(b)
Before 1930, many deaths were due to infectious
disease. Describe and explain one piece of evidence
from the graph which supports this statement.(2)
(c)
Give one way in which the demographic transition
shown in this graph differs from that which occurred in
the United Kingdom. (1)
(Total 6 marks)
Answer
(a) (i)Curve showing constant population until approx 1920;
Increases after this and does not level out;
2
(ii)
Immigration and emigration/migration;1
(b)
Death rate prone to large fluctuations/spikes;
Representing spread of disease during epidemics; 2
(c)
Demographic transition in Mauritius occurs over
shorter period of time/
Birth rate not stabilised at end/occurred earlier in UK; 1
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90
The table shows some information
about the populations of Japan and
Nigeria.
80
70
60
50
Age / years
(a)
The diagram shows a
population pyramid for Japan in
1999.
40
30
20
On the diagram, sketch the population pyramid
as you would expect it to appear in 2015.
10
(2)
Males
Females
Numbers
Country Population Estimated
Fertility
in 1999/
population
rate/
millions
in 2015/
children per
millions
woman
Japan
126.5
126.1
1.4
Nigeria
108.9
153.3
5.1
Life
expectancy
at birth/
years
80
Under-5
mortality/
deaths per
1000
4
50
187
(b)
(i)
Use information in the table to explain why the
population of Nigeria is expected to increase to over 150
million by 2015. (2)
(ii)Suggest and explain two factors that could result in the actual
increase in the population of Nigeria being less than estimated.
1 .......................................................................................................
2 .......................................................................................................
(2)
(Total 6 marks)
Answer
(a) Diagram shows:
narrower base;
increase in numbers of older age groups/ straighter sides;
2
(b)(i) High fertility rate;
higher than replacement rate of 2.0;
not balanced by under-5 mortality;
ref. to life expectancy greater than reproductive life; 2 max
(ii) Disease/AIDS - affecting people of reproductive age
increasing child mortality;
shortage of resources/starvation - increasing as population rises;
improved standard of living / contraception, so fewer children born
effects of war, reducing number of parents, or causing
starvation/shortage of resources;
(Allow 1 mark for 2 factors, without explanations)
2 max
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