Science Notes for all Year 8 Topics (Includes everything)

Unit 1

1.1 – Interactions Between Organisms in
Ecosystems
- The Biosphere and Ecosystems

o Biosphere
 Describes the living component of the earth
 Made up of all the living organisms found within the kingdoms of life
 Bacteria
 Protozoa
 Fungi
 Plants
 Animals
 Extends to any place on the earth where life exists
 Can be thought of as the link between:
 Atmosphere
 Lithosphere
 Hydrosphere

o Ecosystems
 Made up of all the biotic and abiotic factors and the interactions
between the two in an area
 Biotic factors are all the living conditions
 Abiotic factors are all the non-living conditions
 Wetlands ecosystem
 Not made up just the plants that live there
 Includes:
o What animals eat
o Where the different organisms live
o The climate
o The water
o Nutrient availability

 Made up of:
 Habitats
o A particular area where a group of different organisms
live
o Area has similar abiotic conditions
o Vary in size depending on the amount of:
 Food
 Water

,  Shelter
o Must supply all the needs of the populations
 If they are not met, the populations will move
to a different habitat or die out
 Population
o All the individuals of a particular species living in the
same habitat
o Multiple populations (species) make up a habitat
 Community
o Describes the living factor of the habitat
o Each habitat has different mixtures of plants and
animals
o Basically the ‘mixture’ of animals in a habitat

o Benefits of ecosystems
 Water, oxygen, CO2 and other chemicals cycle through the ecosystem
with the help of the biosphere
 Plants and animals contribute to the filtering and cleaning of water in
ecosystems
 Root systems act like filters which trap sediment and some
pollution
 Aquatic creatures (e.g anemone) filter microscopic particles
from the water to feed on, which clean the water

 Animals help with pollination
 Some plants attract insects and birds with brightly coloured or
strong-smelling flowers
 Animals eat the sweet nectar and get dusted with a powder
called pollen
 When the animal moves to the next plant, it transfers the
pollen to it
 Pollen helps fertilise the plants
 More than 70% of plant species are pollinated by animals

- Food Chains and Food Webs

o The Sun – source of energy on earth
 Most organisms’ primary energy source is the sun
 While available to all organisms, not all can utilise it
 Photosynthesis
 All plants, some bacteria, and some protozoa use it
 Used to convert Sunlight into glucose
o The energy in the chemical bonds between the atoms
● The energy from glucose can be obtained slowly through
cellular respiration
(Glucose and Oxygen = Water, Carbon Dioxide and Energy)

, o Not all cells can photosynthesise but all living cells
respire, which means glucose is a vital source of energy
for the entire ecosystem


o Glucose – transferable energy
 Plants
 Use the glucose they produce for their own cellular functions
(growth, repair)
 Store excess glucose for the future
 Plants are autotrophic
o Make their own energy
o Autotrophs are also called producers
o ‘Auto’ = self ‘trophic’ = nutrition

 Transferring energy
 The glucose and its energy are passed on to any organism that
eats the plant
 Heterotrophs
o Can’t produce their own glucose
o Must eat something to obtain their energy
o Also called consumers
o ‘Hetero’ = other’ ‘trophic’ = nutrition
 Energy in the form of glucose moves through ecosystems as
organisms eat each other

o Food Chains
 Diagram
 Represents the path energy can take from producers to
consumers
 Shows a list of organisms in the order of what eats what
 Arrows between each organism to represent the flow of
energy
 Chain
 Must start with a producer
o Make the original glucose
o Type of producer varies across ecosystems
o Could be:
 Grass
 Massive tree
 Seaweed
 Microscopic phytoplankton

 Consumers are then named according to what order they eat in
o Order of consumers:
 First-order / primary consumer
 Second-order / secondary consumer

,  Third-order / tertiary consumer
 Etc.

 Apex / Top predator
 Detritivore or decomposer

 Also named on what they eat
o Herbivores
 Eat plants
 Eat other producers
o Carnivores
 Only eat other consumers
 Highest carnivore in the chain is called the ‘top
predator’
o Omnivores
 Eat plants
 Eat animals
o Detritivores
 Usually small invertebrate animals
 Maggots
 Worms
 Insects
 Eat dead and decaying matter
o Decomposers
 Organisms like bacteria and fungi
 Break down dead matter into basic chemicals
 Return them to the soil, air or water
 Chemicals can be absorbed by plants
through their roots
 They are then recycled back to the start
of a new food chain

 Possible food chain