Photosynthesis

Photosynthesis is the process where green plants make organic food from carbon dioxide and water using sunlight.

Photosynthesis occurs in the chloroplast. (Mainly in leaf cells)

Sunlight is absorbed by a green pigment called chlorophyll found inside the chloroplast.

Oxygen is also produced during photosynthesis. It is released into the environment where it can be used by other organisms (including plants) for respiration.What is Photosynthesis?

A word equation can be used to summarize the process of photosynthesis as seen below:

What happens to the glucose made by photosynthesis?Some is used in respiration to provide energySome is converted to sucrose & sent from the leaves to other parts of the plant where it is needed. Some is used to make cellulose cell wallsSome is converted to starch & stored in special parts of the plant. E.g. stem, roots, chloroplast

Word Equation for Photosynthesis

Photosynthesis provides energy in food which can be used by other organisms.

Photosynthesis produces oxygen which can be used by other organisms for respiration.Importance of photosynthesis

Experiment

A food chain shows how energy passes from one organism to another in the form of food.

In a food chain, an arrow points from the organism being eaten to the organism doing the eating

It is understood that Primary source of energy in a food chain is the sun Each organism in a food chain occupies a feeding position called a trophic level

A food chain begins with a producer (autotroph) e.g. green plant since it make its own food using sunlight (i.e. producers occupy the 1st trophic level)

Food Chains

Consumer (Heterotroph) an organism that obtains food and energy by eating other organismsTypes of Consumers:

Herbivores (primary consumers) organisms that eat only plants Example: cow

2. Carnivores (secondary consumers) organisms that eat only animals Example: lion

3. Omnivores organisms that eat both plants and animals Example: humans

Example of Food Chain

Activity: Use the Food Chains Above to Complete the table Below:

Terrestrial Food ChainAquatic Food Chain (Freshwater)Aquatic Food Chain (Marine)Trophic LevelProducerPrimary ConsumerSecondary ConsumerTertiary Consumer

Food chains are usually short i.e. i.e. only has about 4 to 5 trophic levels.

Why?Only 10 % of energy is passed on from one trophic level to the next. Therefore there isnt enough energy to support more than 4 -5 trophic levels.

What happens to the other 90% of energy?Some is used by the organismSome is lost as heatSome is lost in indigestible material or waste material

Why are food chains usually short

The flow of energy in a food chain is said to be NON-CYCLIC or Linear, because it is not recycled.

However nutrients like carbon and nitrogen can be recycled in the environment. Therefore nutrient flow is said to be CYCLIC.

Energy Flow vs. Nutrient Flow

Carbon Cycle

Carbon cycle - the cycling of carbon through the environment and living organisms.

Carbon is found in the atmosphere as Carbon dioxide (CO2)Plants, animals and decomposers all release carbon dioxide which was produced by Respiration

Plants absorb Carbon dioxide from the air to use in photosynthesis.

Plants & animals which have died millions of years ago form fossils (i.e. fossilization). Fossils have carbon which can be used as a fuels for energy (i.e. fossil fuel). e.g. crude oil

Carbon dioxide is also produce when we burn substances/fuel (i.e. Combustion)

Carbon Cycle

The Nitrogen Cycle - the cycling of nitrogen through the environment and living organisms.

Nitrogen Cycle

1.Nitrogen fixation the conversion of nitrogen into nitrates. This occurs during lightning and by the action of nitrogen fixing bacteria living either in the soil (or in the roots of legumes e.g. red bean plant)

2. Decomposition Proteins in dead organic matter is converted to ammonium compounds by micro-organisms called decomposers (fungi + bacteria)

3. Nitrification the conversion of ammonium compounds in to nitrites and nitrites into nitrates. This is done by the nitrifying bacteria.

4. Denitrification the conversion of nitrates back into nitrogen. This is done by denitrifying bacteria.

Processes involved in the Nitrogen Cycle:

The water cycle describes the continuous movement of water on, above and below the surface of the Earth.

Water Cycle

Evaporation energy from the sun converts water from a liquid to a gas/water vapor

Transpiration the loss of water vapor from plants

Respiration water is produced during respiration

Condensation water vapor cools in the atmosphere and condenses into water droplets forming clouds

Precipitation water is released from clouds as rain, snow or hail

Surface run off the water flowing over the earths surface

Percolation the seeping of surface water into the soilProcesses involved in the Water Cycle