ECOLOGYStudy of living things in their environment

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.

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.

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.

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

FOOD CHAIN

Shows the direction of energy flow from one specie to another.

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.

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%

TROPHIC LEVEL & ENERGY FLOW

As the trophic level increases, the energy flow decreases by 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.

ENERGY & THE ECOSYSTEM

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).

THE GREEN HOUSE EFFECT

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.

EVENTS IN GREENHOUSE EFFECT1. 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.

THE CARBON CYCLE

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.

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.

POPULATIONS

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

SIGMOID POPULATION GROWTH CURVE

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

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