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The Variety of Living Organisms (Bacteria (Cell structure: (Cell wall,…
The Variety of Living Organisms
Plants
All plants are multicellular
Main distinguishing features:
Cells contain chloroplasts
They carry out photosynthesis
Have cell walls made out of cellulose
Can make starch – storage carbohydrate often found inside cells
Can make sucrose – transported around the plant and sometimes stored in fruits and other plant organs
Animals
Include vertebrates – have a vertebral column – and invertebrates
60% of animals species are insects
All animals are multicellular
Distinguishing features:
Cells lack cell walls – allows them to change shape
Gain nutrition by feeding on other animals or plants
Movement often involves coordination by a nervous system
Use
glycogen
as their storage carbohydrate
Fungi
Include mushrooms, toadstools, mould
–> these are multicellular
Also includes yeast – unicellular
Live everywhere – surface of fruits, in soil, water, on dust in the air
Have large vacuole
Cells have cell walls made of
chitin
Structure:
Fruiting body
: the reproductive structure of the organism
(eg. mushroom, toadstool)
Hyphae
: fine thread-like filaments under the soil
(mould: network of hyphae with no fruiting body)
The whole network KA
mycelium
Mucor:
Hyphae have cell walls surrounding cytoplasm
Cytoplasm contains many nuclei – not divided up into separate cells
Spore lands on food => hypha grows out from it
–> hypha grows and branches repeatedly until the mycelium covers the surface of the food
–> hyphae secret digestive enzymes on to the food, breaking it down into soluble substances which are then absorbed by the mould
Saprotrophic nutrition
: digestion taking place outside of the organism.
–> Enzymes secreted for this purpose KA
extracellular
enzymes
Protoctists
A mixed group of organisms that don't fit into plants, animals or fungi (or bacteria)
Most are unicellular
Some look like animals cells, KA
protozoa
eg.
Amoeba
which lives in pond water,
Some have chloroplasts and carry out photosynthesis, KA
algae
–> most are unicellular, some, eg. seaweeds, are multicellular and can grow very large
Some are pathogens, eg.
plasmodium
which causes malaria
Eukaryotic and prokaryotic organisms
Eukaryotic means 'having a nucleus' – cells contain a nucleus surrounded by a membrane, along with other membrane-bound organelles, eg. mitochondria, chloroplasts
Prokaryotic means 'before nucleus' – organisms made of simpler cells which have no nucleus or mitochondria, mainly bacteria
Bacteria
Unicellular – cells are thousands of times smaller than animal cells
Three basic shapes: spheres, rods, spirals – all have a similar internal structure
All have cell walls made of
peptidoglycan
–> some species have another layer KA a
capsule
or slime layer which give extra protection
Inside of cell is the cytoplasm, containing:
A single chromosome in a circular loop
Plasmids – small circular rings of DNA
–> present in 75% of species
Chlorophyll
–> present occasionally
–> allows photosynthesis to take place
Cell structure:
Cell wall
Cell membrane
Cytoplasm
Chromosome
Maybe: plasmids
Maybe: flagellum
Maybe: slime capsule
Maybe: chlorophyll
Nutrition:
Some (with chlorophyll) can photosynthesise
Most feed off other organisms
–> many are decomposers
Can be pathogenic
Viruses
All viruses are parasites and can only reproduce inside living cells
Cell in which the virus lives KA the
host
Between 0.01 and 0.1 micrometres in diameter
Structure:
Core of genetic material – can be DNA or RNA
Surrounded by a protein coat
Sometimes a membrane KA an
envelope
can surround the virus
–> not made by the virus –> stolen from the surface membrane of host cell
Do not respire, excrete, move, grow, do nutrition or do sensitivity
Reproduction: takes over host's genetic machinery to make more virus particles –> host cell dies –> particles released to infect more cells
Cause colds, measles, mumps, polio, rubella