Compare…
Elephant reproduction
THINK!
How do you set out a compare question?
vs
Mantis reproduction
Population growth
Reproductive Strategies
Learning outcomes
Describe the principles associated with survivorship curves including,
K-strategists and r-strategists.
You should all be able to:
• Identify the characteristics of K- and r-strategists
Most of you should be able to:
• Describe the association between these characteristics and
survivorship curves
Some of you might be able to:
• Interpret the more complex features of survivorship curves including logarithmic scales.
Different reproductive strategies!!
K-strategists
Slow growing organisms, limited by the carrying capacity (K)
of an environment.
r-strategists
Characterised by rapid growth followed by decline – tend to
inhabit unpredictable rapidly changing environments. Have a
fast rate (r) of increase.
K- and r-strategists
r-strategists
K-strategists
Place the statements in the correct
column!
Rapid growth
Long life
Adapted to
stable
environment
High
investment in
individual
offspring
Early maturity
Late maturity
Many small
offspring
Fewer large
offspring
Little parental
care or
protection
High parental
care and
protection
Little
investment in
individual
offspring
Examples:
annual plants,
flour beetles,
bacteria
Slower growth
Adapted to
unstable
environment
Pioneers,
colonizers
Later stages of
succession
Niche
generalists
Niche
specialists
Short life
Examples:
trees,
albatrosses,
humans
Check yourself!
r-strategists
K-strategists
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Short life
Rapid growth
Early maturity
Many small offspring
Little parental care or protection
Little investment in individual offspring
Adapted to unstable environment
Pioneers and colonisers
Niche generalists
Prey
Regulated mainly by external factors
Lower trophic level
E.g. annual plants, flour beetles,
bacteria
Long life
Slower growth
Late maturity
Fewer large offspring
High parental care and protection
High investment in individual offspring
Adapted to stable environment
Later stages of succession
Niche specialists
Predators
Regulated mainly by internal factors
Higher trophic level
E.g. trees, albatrosses, humans
Survivorship curves
Look at the graph on
your handout!…
Group discussion:
What is shown on the
x- and y- axes?
What is unusual
about the y-axis?
Discuss in pairs….
Now annotate your graphs with what we have discussed!
Almost
all individuals
Look
at the 3survive
for their potential lifespan and
survivorship curves…
then die almost simultaneously
(K-strategists)
Which curve do you
think represents a Kstrategist
and
which
Individuals
that lie
between
the
twoan
extremes
(C-strategists). This
r-strategist?
curve is rather rare. It represents
species that have an equal chance
of dying at any age.
Most individuals die at a very
young age but those that
survive are likely to live for a
very long time (r-strategists)
Test yourself
1. Explain whether K- or r-strategists would be
more likely to be regulated by densityindependent limiting factors e.g. the
weather.
2. Describe and explain the shape of the
survivorship curve for K-selected species.