Topic 3 - Wood Wide Web

Question 1

Explain the difference between an autotroph and heterotroph, stating how they gain nutrients.

Answer 1

Autotrophs feed themselves to meet their energy requirements; rely on chlorophyll-based photosynthesis

Heterotrophs rely on other organisms to feed them; they ingest complex organic molecules that have been synthesised by another organism

Question 2

What is a simple sugar? Give an example.

Answer 2

A carbohydrate molecule with between 3 - 7 carbon atoms, that free floats in a cell.
Example - fructose.

Question 3

What is a disaccharide? Give an example.

Answer 3

A pair of simple sugars that have joined to form a larger molecule.
Example: sucrose, lactose, maltose.

Question 4

What is the difference between an oligosaccharide and a polysaccharide? Give an example.

Answer 4

An oligosaccharide is a short chain of carbohydrate sugars, for example fructans.

Polysaccharides are more common and form longer chains for sugars for storing carbohydrates.
Example: starch (plants) and glycogen (animals).

Question 5

What is TAG?

Answer 5

TAG (Triacylglycerol) is a lipid. It is a chain of three fatty acids linked by ester links to a glycerol molecule.

Question 6

Name three approaches for gaining products from other organisms, giving examples of types of organism in each category.

Answer 6

Saprotroph - eats of already dead material, eg. detritivore, scavenger

Necrotroph - kills living material to feed, eg. carnivore (lion)

Biotroph - feeds off living material, eg parasite (tapeworm)

Question 7

How do animals (eg. carnivores) prevent excess nitrogen amine groups becoming toxic, after eating lots of protein?

Answer 7

Amine groups combine with CO2 to create urea, which is neutral in pH and can be excreted into the environment directly or after being extract from blood by the kidneys

Question 8

Give three reasons why organisms tend to excrete rather than store excess nutrients.

Answer 8

Excess weight can mean they lose a competitive advantage.

Many are toxic in higher levels, eg. nitrogen can raise pH levels and interfere with metabolism.

Chlorides interfere with osmosis, and high levels of solutes affect movement of proteins across cell membranes.

Question 9

What is Liebig’s law of the minimum?

Answer 9

It is that the essential nutrient that is in shortest supply with limit growth.

Question 10

What is altruism?

Answer 10

Where an organism helps another without any direct benefit to itself.

Question 11

What is co-evolution?

Answer 11

It is when two different species evolve in parallel, because the relationship benefits them both (mutualism).

Question 12

What is amensalism?

Answer 12

A species does not benefit directly from its interaction with another species, but the interaction has a clear disadvantage for the other species.
(0,-)

Question 13

What interaction is meant by (+,0)

Answer 13

Commensalism. This is where a species shares space with another and is not harmed by it.

Question 14

Which [three] groups of organisms are unikonts?

Answer 14

Animals, fungi and slime moulds.

The cells have just one flagellum.

Question 15

What is the feature of bikonts and which three organism groups are they?

Answer 15

Cells have two flagella.

Flowering plants, mosses and algae.

Question 16

What is saprotrophy?

Answer 16

It’s the ability to use dead organic matter as a food source.

Question 17

How is necrotrophy different from saprotrophy?

Answer 17

In nectrotrophy, a fungi first kills live cells and then ingests them, whereas in saprotrophy the fungi consumes organic matter that is already dead.

Question 18

What are the THREE processes by which a fungus can extract nutrients - give a brief explanation.

Answer 18

1. Saprotrophy – dead organic matter
2. Nectrotrophy – kill live cells, then consume
3. Biotrophy – extract from living tissues

Question 19

What are the two tactics that plants have to defend against fungi?

Answer 19

Hypersensitive response - release hydrogen peroxide to isolate the infection by killing the fungi and cells its on.

Produce anti-fungal toxins that interfere with the fungi’s metabolism and/or degrate fungal cell walls.

Question 20

What is the name of the enzyme at the heart of the C3 pathway?

Answer 20

Rubisco

Question 21

What causes photoinhibition and what damage can it do?

Answer 21

Too much light means dark reactions can’t occur fast enough, leading to an excess of ATP.
This can reduce the efficiency of photosynthesis by damaging chlorophyll molecules and their membranes.

Question 22

What is a plastid?

Answer 22

It is a cell organelle that has a specialised metabolic process. They are only found in eukaryotes.

Question 23

What are the main divisions of mycorrhiza based on?

Answer 23

Does the fungi penetrate the plants root or not?
If yes = endomycorrhiza.
If no = ectomycorrhiza.

Question 24

In addition to autotrophs, that gain their energy from the sun, what are the THREE other types of plant and how to they gain their energy?

Answer 24

Hemi-parasitic - take some nutrients from other plants but still photosynthesises (autotroph + biotroph)

Parasitic - take nutrients are carbs from other plants

Carniverous - consume other organisms (autotroph + necrotroph)