1) Nature and Variety of living organisms Flashcards
Characteristics of living organisms
MRS GREN
-movement
-respiration
-sensitivity
-growth
-reproduction
-excretion
-nutrition
Living organism classification
Eukaryotes:
-animals
-fungi
-plants
-protoctists
Prokaryote:
-bacteria
Plants
-multicellular
-contain chloroplasts and carry out photosynthesis
-convert simple organic molecules water and carbon
-into complex organic compounds:
–cellulose - cell walls
–starch - transported around the plant and sometimes storedin fruits, other plant organs
Animals - vertebrates/ invertebrates
-vertebrates (have a backbone): fish, amphibians, reptiles, birds, mammals
-invertebrates (no backbone): sponges molluscs, worms, starfish, insects
Animals
-multicellular
-never contain chloroplasts
-gain nutrition by feeding on other animals/ plants
-store carbohydrate in their cells as glycogen
Animals - movement
-lack cell walls - allow cells to change shape - organisms can move from place to place
-often involves coordination by a nervous system
Fungi
-multicellular - mushrooms, toadstools, moulds
-unicellular - yeasts
-cannot photsynthesise
-cell walls made of chitin
Structure of fungi
-fruiting body/ reproductive structure: mushroom/ toadstool
-hyphae: fine thread like filaments called hyphae under the soil
Fungi - mould
Mushroom without the fruiting body
-consists of the network of hyphae
-whole network - mycelium
-feed by absorbing nutrients from the dead material
Fungi - mucor
-hyphae of mucor have cell walls surrounding their cytoplasm
-cytoplasm contains many nuclei - hyphae are not divided up into separate cells
How mold grows on food
-spore from mucor lands, hypha grows out from it
-grows and branches again and again until the mycelium covers the surface of the food
-hyphae secrete digestive enzymes onto the food
-breaks it down into soluble substances such as sugars - absorbed by the mould
-eventually food is used up
-mould must infect another source by producing more spores
Saprotrophic nutrition
When an organism feeds on dead organic material and digestion takes place outside of the organism
-extracellular enzymes: enzymes secreted out of cells for this purpose
Protoctists
-mixed group of organisms, don’t fit in others
-amoeba, like animal cells - lives in pond water
-chlorella - have chloroplasts
-plasmodium - causes malaria
Eukaryotic organisms
Have organelles within cell
-Basis for unicellular, multicellular
Prokaryotic cells
No organelles
-only for unicellular
Bacteria
-small, single celled organisms
-cells are much smaller than eukaryotic organisms
-basic shapes: spheres, rods, spirals
-many are important decomposers
-used by humans to make food - lactobacillus bulgaricus
-some are pathogens - cause disease
Bacteria structure
-Cell wall
-Capsule/ slime layer
-Cell membrane
-Cytoplasm
-No nucleus (prokaryotic cell)
-chromosome (nucleoid)
-Flagella
-plasmid
-some have chlorophyll
Bacteria - cell wall
-protects bacterium/ keeps shape of the cell
-made of a complex compound of sugars and proteins - peptidoglycan
Bacteria - capsule/ slime layer
-another layer outside cell wall
-give extra protection
Bacteria - chromosome
-genetic material in a single chromosome
-loose in the cytoplasm
-form a circular loop
Bacteria - flagella
-some bacteria can swim, propelled through water by corkscrew-like movements of flagella
-don’t have flagella, can’t move
Bacteria - plasmid
-small circular rings of DNA
-carry some of bacterium’s genes
Viruses
-smaller than bacteria
-parasitic and can reproduce only inside living cells
-infect every type of living organism
-wide variety of shapes and sizes
-no cellular structure
-have a protein coat and contain either DNA or RNA
Viruses - as a parasite
-envelope stolen from surface membrane of host cell may surround a virus particle
-infect plant cells - e.g. tobacco mosaic virus interferes with the ability of the tobacco plant to make chloroplasts - cause mottled patches to develop
Viruses - reproduction
-virus reproduces by entering the host cell, takes over the host’s genetic machinery to make more virus particles
-after many virus particles have been made, the host cell dies
-particles are released to infect more cells
Viruses - diseases
-e.g. influenza, colds, measles, mumps, polio
-usually the body’s immune system destroys the virus and the person recovers
-if it is not destroyed quickly enough - may cause permanent damage/ death
-virus may attack cells of the immune system - e.g. HIV causes AIDS
