Transcript Biotic Interactions

Costs, benefits and
consequences of interactions
5.2 Interactions with the
environment
What can an organism do if their
external environment changes?
1. Resist or tolerate the change (eg. feels cold but
doesn’t die!)
2. Regulate the internal equilibrium as a response to
the change (eg. Homeostasis)
3. They can move away to an area that is more suitable
4. Adapt - an ORGANISM can’t adapt but the species
can over a very long time
Resistance or toleration of change
100
Zone of
resistance
Zone of tolerance
Zone of
resistance
% survivability
0
Low
High
Environmental condition or resource
Key point - there are limits to the ability to tolerate change.
Tips for Note-taking
1. Have the internet to hand to check words and
read about ideas.
2. Include definitions.
3. Include examples.
4. Group information – use bullets or numbers to
make lists
5. Mind Map it
6. Digest the information then explain first using
complex terminology then in simple terms.
7. Try to link ideas together
8. Summarise what you have just learned.
Example - Life in deserts
Adaptations to cope with dry conditions:-
• see box 5.2.1 p27 and make notes
Points to consider:
1. What are the 2 main problems facing
organisms in this environment?
2. Why is this so difficult to overcome?
3. List any totally new terms at the end of
your note.
Costs, benefits and
consequences of
interactions
5.3 Variation in life history
Life history is organised to suit specific needs
K - strategists (large mammals, some birds)
Stable predictable
environment, climax
community
• long lifespan
• slow growing
• slow reproduction rate
r - strategists (bacteria, insects, weeds)
Changing
environmental
conditions, pioneer
species
• early reproduction
• high rate of population
increase
• rapid development
Reproduction styles
K - strategists
Multiple breeding
opportunities
• e.g. humans or trees
Narrowcast
fertilisation
• small numbers of gametes
produced
• survival rate is high
• lots of parental care
r - strategists
Single breeding
opportunities
• e.g. salmon, squid, eels
Broadcast
fertilisation
• huge numbers of gametes
produced
• survival rate is low
• little or no parental care
Life History Adaptations to Cope with environmental Change
Seasonal change
requires a period
of rest
• dormancy (period of ‘rest’)
• diapause (period of
cessation of growth)
‘Rest’ of either type can be
Predictive
• occurs in advance of adverse
conditions
• where seasons are predictable
• genetically determined
Consequential
• occurs when conditions
become suddenly adverse
(usually K - strategists)
(usually R - strategists)
Types of Dormancy
Facultative
(consequential)
• optional, occurs when
conditions become adverse
Obligate
(predictive)
• associated with a stage in
development
Hibernation
(O or F)
-inactive state where metabolism
slows down to conserve energy
Resting spores
(F)
- bacteria and fungi
Diapause
(O)
- stage in insect life cycle where
growth stops completely (pupa)
Aestivation
(F)
- inactive period during hot dry
Today (and Homework)
1.
Complete Scholar online activity “Life history of
Chlamydomonas”
2. Complete Scholar online activity “Life history of Taenia spp”
3. Using the examples of fish and elephants, compare the life
histories of an r-selected species and a K-selected species. (15)
Hand in next week.
4. Explain the function of dormancy and describe the different
types. In your jotter - don’t hand in.
5. For next week (Monday) reading on “Homeostasis”
- Monograph Pg 30-32