Chapter 13
Chapter 13 Populations and sustainability
By the end of this session I should be able to:
(a) explain the significance of limiting factors in
determining the final size of a population;
(b) explain the meaning of the term carrying
capacity;
(c) describe predator–prey relationships and their
possible effects on the population sizes of both the
predator and the prey;
(d) explain, with examples, the terms interspecific
and intraspecific competition;
(e) distinguish between the terms conservation and
preservation (HSW6a, 6b);
Bacterial Growth Curve
In a closed system, the
organisms will
eventually produce toxic
by-products and die
because the carrying
capacity of the growth
medium has been
exceeded.
http://pathmicro.med.sc.edu/fox/growth_c.jpg
World Population Density, 2012
www.nationsonline.org
World Population Density –
Another View
National Geographic Atlas of the
World, Eighth Edition
WATCH! 2013 Population video http://www.youtube.com/watch?v=sc4HxPxNrZ0
Carrying Capacity
• The population that an area will support
without undergoing environmental
deterioration.
• The carrying capacity of an environment tends
to limit population size.
• Food availability, reproductive behaviour, and
infectious diseases tend to keep animal (inc
human) populations in check.
WATCH ME!
http://www.youtube.com/watch?v=BSVbdaubxxg
In reality what does the carrying capacity
look like?
Abiotic factors are the non-living Components of the
Environment
• Abiotic factors include:
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Sunlight
Water
Temperature
Wind
Soil/substrate (edaphic)
Special events such as:
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Fires
Hurricanes
Floods
Volcanic eruptions
Tsunamis
Biotic Factors  A living organism is also affected by the
living components of its environment.
• Predators feed on members of the population.
• Microbes can bring diseases. (If time travel were possible,
and you could be transported to the Cretaceous Era to look
at dinosaurs, don’t be afraid of Tyrannosaurus, fear the
microbes. You would have no immunity to them!!)
• There may be competition for nesting space.
• Plants may compete for the light needed to carry out
photosynthesis.
• There are many other biological factors determining the
success of an individual or species.
• Competition exists for available food resources.
Predator – Prey Relationships: A Description
•
WATCH ME!
http://www.youtube.com/watch?v=CsfJL-IIVz4
(Madler, 1998)
The predator’s abundance curve almost always lags
behind that of the prey. WHY?? (2 marks)
In reality the pattern is not always followed!!
Circle areas on the graph where the is the case.
Discussion pairs – 2 minutes
Suggest reasons for the
areas that you have circled
on the graph where the
typical predator prey pattern
is not followed. (3 marks)
Describe and explain the trend on the graph below. (5 marks)
http://www.youtube.com/watch?v=D1aRSeT-mQE
Competition key terms  4 Minutes
Key Term
Compete
Intraspecific
Competition
Interspecific
Competition
Niche
Definition
Plant example
Animal example
Sampling using transects
Transects: LINE, BELT, CONTINUOUS, INTERRUPTED
Procedures & equipment to consider when studying
succession
Distinguish between a line transect and a belt transect.
Outline the advantages and limitations of using a frame quadrat.
Outline the advantages and limitations of using a point quadrat.
Studying succession – normally involves use of
transects
Describe how you would investigate plant diversity along a sand dune.
For each scenario use pages 190 & 191
Scenario 1: Using a gridded quadrat along a line transect (8 marks)
Scenario 2: Using a point quadrat along a belt transect (8 marks)
Studying succession – normally involves use of
transects
Describe how you would investigate plant diversity along a sand dune.
For each scenario use pages 190 & 191
Scenario 1: Using a gridded quadrat along a line transect (8 marks)
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11
[8]
ref to setting grid/area to be sampled;
suitable reason for method chosen/ref line transect;
ref to repetition of line transects;
use of quadrats;
use of appropriate sized quadrat;
details of co-ordinates for quadrat placing;
identify species/use of keys;
presence or absence in quadrat;;
measure % cover/use of appropriate scale; e.g.ACFOR
ref to analysis of data/use of kite diagram;
AVP; ref to relevant statistical analysis, e.g. Spearmans Rank Correlation
max 7
QWC - clear well-organised answer using specialist terms
1
Studying succession – normally involves use of
transects
Describe how you would investigate plant diversity along a sand dune.
For each scenario use pages 190 & 191
Scenario 2: Using a point quadrat along a belt transect (8 marks)
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Details of positioning of belt transect (90 degrees from shoreline)
Definition of belt transect
Why a belt transect is suitable
Description of placement of point quadrat (every 1m/5m)
Description of use of point quadrat e.g. species present/not present under pin
Identification of species (key)
Reference to analysis of data e.g species frequency