quick notes for IB Biology revisions

1. ECOLOGY
Study of living things in their environment

2. INTRODUCTION
 Energy reaching the green plants as light is
transferred to the chemical energy of nutrients
during photosynthesis.
 During feeding, energy is transferred from
organism, but is eventually returned to the
environment as heat.
 Cell respiration
 ATP is the energy currency in cells and
organisms.
 Light is the initial energy source for almost ALL
communities.

3. COMMUNITIES AND ECOSYSTEMS
 Specie – a group of organisms that can interbreed
and produce fertile offspring.
 Habitat- the environment in which a specie normally
lives or the location of a living organism.
 Population – a group of organisms of the same
specie who live in the same area at the same time.
 Community – a group of populations living and
interacting with each other in an area.
 Ecosystem - a stable, settled unit of nature
consisting of 1 a community of organisms interacting
with each other, and 2 with their surrounding physical
and chemical environment.

4. FEEDING RELATIONSHIPS
 Autotroph – organisms that synthesize their own
organic molecules from simple inorganic substances
(producers – plants)
 Heterotroph – organisms that obtain organic
molecules from other organisms (consumers,
detritivores, saprotroph)
 Consumer – an organism that ingest other organic matter
that is living or recently killed.
 Detritivore – an organism that ingest non living organic
matter.
 Saprotroph – an organism that lives on or in nonliving
organic matter, secreting digestive enzymes into it and
absorbing the products of digestion.

5. FEEDING RELATIONSHIP:
PRODUCERS AND CONSUMERS
 Plants and photosynthetic organisms -
producers
 Herbivores – feed on plants; primary
consumers
 Carnivores - feed on primary consumers;
secondary consumers.
 Tertiary carnivores – feed on secondary
consumers

6. FOOD CHAIN
 Shows the
direction of energy
flow from one
specie to another.

7. FOOD WEB
 This is a diagram
that shows ALL the
feeding
relationships in a
community with
arrows which show
the direction of the
energy flow.
Identify the tertiary consumers.

8. TROPHIC LEVELS
 The trophic level of an
organism is its position in
the food chain.
 Trophic level and Energy
flow:
 Producers – 100%
 Primary consumers – 10%
 Secondary consumers – 1%
 Tertiary consumers …. –
0.1%

9. TROPHIC LEVEL & ENERGY FLOW
 As the trophic level increases, the energy
flow decreases by 10%.

10. ENERGY AND THE ECOSYSTEM
 Energy flows from producers to primary
consumers, to secondary consumers….
 Energy is LOST in each trophic level in the
form of HEAT through RESPIRATION,
FECES, TISSUE LOSS and DEATH.
 Some of the lost energy is used by
detritivores and saprotrophs. Detritivores and
Saprotrophs lose energy through cellular
respiration also.

11. ENERGY & THE ECOSYSTEM

12. ENERGY IS LOST BUT NUTRIENTS ARE RECYCLED
 Energy is not recycled. They are constantly supplied
though LIGHT energy.
 Energy is lost from the ecosystem in the form of heat
through cell respiration.
 Energy loss accounts for 80-90% of energy loss from
one trophic level to another.
 Nutrients must be recycled as there is only a limited
supply of them. (role – saprophytic bacteria, fungi)
 Nutrients are absorbed by the environment, used by
organisms and then returned to the environment
(death and decomposition).

13. THE GREEN HOUSE EFFECT

14. THE GREEN HOUSE EFFECT
 The greenhouse effect is a process by which
thermal radiation from a planetary surface is
absorbed by atmospheric greenhouse gases, and is
re-radiated in all directions.
 Cause – heat energy from the sun is trapped by
greenhouse gasses (CO2 ) in the atmosphere and is
reflected back to the earth.
 Normally, heat from the sun is reflected back from the
earth’s surface.
 Result - the average surface temperature is higher
than it would be if direct heating by solar radiation
were the only warming mechanism.

15. EVENTS IN GREENHOUSE EFFECT
1. The incoming radiation from the sun is short wave UV
and visible radiation.
2. Some of this radiation is absorbed by the earth’s
atmosphere.
3. Some of the radiation is reflected back into space by the
earth’s surface.
4. The radiation which is reflected back into space is
infrared radiation and has a longer wavelength.
5. The greenhouse gases in the atmosphere absorb some
of this infrared radiation and reflect it back towards the
earth.
6. This causes the green house effect and results in an
average mean temperatures on earth.
7. A rise in greenhouse gases results in an increase in
greenhouse effect which can be disastrous for the
planet.

16. THE CARBON CYCLE

17. THE PRECAUTIONARY PRINCIPLE
 “if the effects of a human-induces change
would be very large, perhaps catastrophic,
those responsible for the change must prove
that it will NOT do harm BEFORE
proceeding.

18. CONSEQUENCES OF A A GLOBAL TEMPERATURE
RISE ON ARCTIC ECOSYSTEM
 The arctic ice cap may disappear as glaciers start to
melt and break up into icebergs.
 Species adapted to temperature conditions will
migrate north which will alter food chains and have
consequences on higher trophic levels.
 Extinction of arctic species due to melting of ice caps.
 Melting of ice will rise sea levels and flood low lying
areas of land.
 Extreme weather events such as storms might
become common and have disastrous effects on
certain species.

19. POPULATIONS

20. FACTORS AFFECTING POPULATION SIZE
 Natality – population size increase thru
offsprings
 Immigration – population size increase as
individuals move into an area from
somewhere else.
 Emigration – population decrease:
individuals move out
 Mortality – population decrease: due to death
– sickness or predation

21. SIGMOID POPULATION GROWTH CURVE

22.  Exponential phase
 Rapid increase in population growth
 Natality exceeds mortality rate
 Emigration ex
 Abundant resources available
 Diseases and predators are rare
 Transitional phase
 Natality starts to fall and mortality starts to rise
 Decrease in resources
 Increase in predators and diseases
 Population still increases but at slower rate
 Plateau phase
 No more population growth – constant
 Natality = mortality
 Population has reached the CARRYING CAPACITY of the environment
SIGMOID POPULATION GROWTH CURVE

23. FACTORS LIMITING POPULATION INCREASE
 Shortage of resources
 Increase in predators
 Increase in diseases and parasites