4.5 Food Chains and Food webs

4.5a Food chains
• Food chains=links producer to other consumers
• 1 organism per tropic level
• Cannot show animals that are omnivore, or 2 tropic levels
• Show the flow of matter/energy

4.5b Food webs
• Shows ecosystem
• Shows interaction (feeding) of a community of organism
• Feeding at different tropic levels
• Organisms have multiple predators/multiple prey
• It is a link of many different food chains

4.4 Tropic Levels

• Tropic= to feed
• Producers at the bottom of the food chain(plants etc)
• Consumers are things that eat other things (animals etc)
• Producers change light energy to chemical energy
• Consumers ea the producer and converts chemical energy to their own chemical energy
• 1st consumer= primary 2nd consumer=secondary 3rd= tertiary
• Decomposers= fungi and bacteria (turns them into nitrates and phosphates)

Ecosystem

4.1 Ecosystem
• Describe the community of organism
• Community of organism: Population of different species, no. of individuals in a particular species, Organism reproduction
• Describe the habitat
Habitat: a biotic factors in that area e.g. Temperature, rainfall, daylight non-biological things)
• Eco-system is a community of organisms that interact with one another in a habitat



4.2 Quadrates
• Quadrates are used to estimate the population size of an organism
• Count the number of individuals in the population
• Quadrate = Square grid used to sample an area in the ecosystem
• Count the number of individuals in the quadrate and repeat a number of times
• Used to find an estimate of population size



4.3 Quadrate sampling
• Quadrate Sampling must be a large sample and random
• Grid system
• Generate random numbers (from online/tables)
• Take sample and count number of individuals(e.g. daisy)
• The bigger the quadrate the better
• About 10 quadrates which is 10% of the actual area
• Make a table with the quadrate number and the number of individuals
• Add up total number of individual organisms then divide by the number of quadrates
• Gives up the number of organisms per m2

3.4 Plant Fertilization notes

• Pollen grain on stigma
• Pollen tube grows down to ovule
• Nucleus travels down tube to ovule and fertilize
• Outside of Ovule forms the seed coat
• Catelydons inside ovule (power pack/food storage)
• Thickening of the walls of ovary to make fruit

3.3b Wind Pollination

• Anther  stigma (by wind)
• Pollen grain adaptation-light weight, wing feature to move through air
• Exposed anther (exposed to the wind)
• Stigma with large surface area to catch pollen (feather like structure)
• In addition- no scent, no petals, no color,

3.3a Insect Pollination

• Pollination by insect
• Pollen (male nuclei) transferred to stigma of another flower
• Attraction of insect to the flower is needed
• Signals to the insect (scents, color petals)
• Value to insects (food nectarines/ pollen protein)

2.81 Photo tropism

• Phototropism= Light Growth Response
• Positive= Growth towards light
• Stem grows upwards
• But if light comes from the side the plant stem bends towards the light
• Plant hormone causes this