Selected habitats

Question 1

Why do rainforests have such high biodiversity?

Answer 1

The abiotic (non living) conditions are relatively constant and ideal for photosynthesis
-warm / hot
-high rainfall
-high light levels

Biotic factors (animals, plants, fungi, bacteria, protists) dominate survival because they have had a long time to adapt to the abiotic conditions, producing unique ecological niches
eg. pollination and seed dispersal
feeding / avoiding predation

Question 2

Why do some plants in the rainforest have leaves which are not green?

Answer 2

The dense rainforest vegetation absorbs most of the available sunlight (blue and red wavelengths are absorbed by chlorophyll and used in photosynthesis. Chlorophyll reflects green wavelengths).
Plants growing on the forest floor often have red, blue or purple pigments which can absorb the green light that reaches the ground.

Question 3

Why are monkeys important for the survival of many tree species?

Answer 3

Trees rely on seed and fruit eating animals to disperse their seeds.
Some seeds may be eaten, but others will be dropped or buried.
Animal dispersed seeds are often much larger than wind dispersed seeds, increasing the chances of the young plant surviving.

Question 4

Suggest 2 ways in which rainforests could be a source of future foods.

Answer 4

1. Rainforest species could be cultivated to produce food.
2. Wild varieties of species that are already cultivated may have genetic characteristics that could be used in breeding programmes.

Question 5

Give 3 ways that rainforests affect the hydrological cycle.

Answer 5

1. vegetation increases interception. Some of this water evaporates and increases rainfall downwind.
2. transpiration (evaporation through stomata) from leaves increases rainfall downwind.
3. leaf litter and surface roots increase infiltration, increasing groundwater levels and reducing runoff.

Question 6

Outline 3 ways that coral polyps obtain their nutrients.

Answer 6

1. photosynthesis symbiotic algae which live inside the polyp cells (this provides about 90% food energy).
2. cilia in polyp tentacles - trap passing planktonic organisms which are then passed into the gut.
3. nematocysts - singing cells kill planktonic organisms swimming nearby.

Question 7

What are the abiotic conditions that tropical coral reefs require for survival?

Answer 7

-warm temp (around 26 degrees)
-bright sunlight for algal photosynthesis
-continual immersion to prevent drying, but not too deep, which would reduce light penetration
-constant salinity
-low turbidity (level of particles in the water), because suspended solids reduce light levels and can clog the cilia and gut.

Question 8

How do coral reefs contribute to the control of climate change?

Answer 8

Coral polyps absorb carbon dioxide from the sea and use it to make calcium carbonate, which is the main component of coral.
This prevents carbon exsolving into the atmosphere.

Question 9

How can we reduce damage to corals from tourists?

Answer 9

• training to reduce fin contact with coral
  -fixed mooring buoys to reduce anchor damage
  -ban souvenir collection
  -reduce spear fishing
  -tourists kept away from turtle nesting beaches
  -litter control
  -tourist developments that don’t destroy mangroves - coral can attach themselves to mangrove roots
  -control of pollution generated by visitors eg sewage

Question 10

How do seagrass beds and mangroves help coral reef conservation?

Answer 10

-trap sediments and reduce water turbidity. Turbidity can kill coral polyps by reducing filter feeding and can reduce photosynthesis by zooxanthellae
-eelgrass beds and mangroves also act as egg laying and nursery grounds for fish that live on the reefs as adults.