Need to know

Question 1

Micro-organism (1)

Answer 1

• mostly invisible to the naked eye

Question 2

pathogen (2)

Answer 2

• a disease causing microbe

- commonly called germs

Question 3

vector (1)

Answer 3

• does not cause disease but spreads infection by conveying pathogens from one host to another

Question 4

saprophyte (1)

Answer 4

an organism that lives on dead or decaying material

Question 5

parasite (1)

Answer 5

an organism that lives on other organisms at the expense of other organisms

Question 6

Roles in maintaining balance in an environment (5)

Answer 6

• plant degraders (clean up dead plants)
• micro-regulators of nutrients (the decomposers absorb the nutrients that would remain in the decaying substance - this allowing animals to gain it by eating the decomposers, also release CO2 and nutrients)
• regeneration of oxygen (cyanobacteria and phytoplankton help in replacing - in some cases - up to 50% of all used oxygen)
• Nitrogen transformers (Nitrifying- bacteria change nitrogen into useable forms)
• biological control agents (can act as natural enemies of pests, pathogens and weeds helping keep the environment healthy and balanced)

Question 7

Symbiotic relationship (4)

Answer 7

• A relationship between species where both benefit (mutualism), one benefits and neither are harmed (commensalism) or one benefits and the other is harmed (parasitism)
• E. Coli (normal gut flora helps digest food - mutualistic - bacteria gain glucose and other nutrients, humans gain vitamin K2 which is needed to form thrombin for blood clotting)
• nitrogen-fixing bacteria (Rhizobium live in the root nodules of legumes - mutualistic - Rhizobium gain glucose and other nutrients, plants gain ammonia used to make amino acids)
• Mycorrhizal fungi and plant roots ( a fungi found in approximately 70-80% of all plants - mutualistic - fungus is provided with glucose, plant gains an increased absorptive surface and protection against pests and diseases - by the hyphae)

Question 8

fungi (Characteristics) (11)

Answer 8

• own kingdom
• decomposers of matter
• anatomical and biochemical features
• everywhere (usually invisible to the naked eye)
• free-living (live in soil, air and dead organic matter)
• heterotrophs
• saprotrophic (feed on decaying or dead waste)
• can be parasitic (athletes foot)
• asexually reproduce
• mostly multicellular (but can be unicellular) eukaryotes
• live in symbiotic relationships with the plants and animals

Question 9

Viruses (characteristics) (6)

Answer 9

• extremely small (only seen with an electron microscope)
• virus (active) virion (dormant)
• not necessarily living organisms (exhibit live characteristics, but do not perform life tasks - breathe, excrete etc.)
• obligate intracellular parasites (can only survive and reproduce inside a living cell)
• always associated with disease
• different shapes

Question 10

bacteria (characteristics) (7)

Answer 10

• most diverse and abundant group
• inhabit practically all environments
• mostly useful but can be harmful
• unicellular and the smallest organisms
• vary in shape
• can exist singly, in chains or in clumps
• can reproduce very quick due to binary fission (in favourable conditions, DNA replicates and segregation occurs simultaneously)

Question 11

protists (characteristics) (6)

Answer 11

• all eukaryotic
• all live in moist environments
• unicellular or multicellular
• microscopic or 100 m long
• heterotrophs or autotrophs
• plant like or animal like