Grade 12 Environmental Studies - Part 3 Competition

Question 1

Define competition:

Answer 1

When two or more individuals compete for the same resources that are in short supply.
Resources such as shelter, space, water, food, light…

Question 2

What can the value be of competition?

Answer 2

Powerful force affecting the growth, distribution and size of populations in nature.

Question 3

Define **intraspecific **competition:

Answer 3

• Occurs between individuals of the SAME species. **
• Includes competition for mates as well as resources.
• Most intense - as members of hte same species have similar habitats and resource requirements e.g. tadpoles competing for food in a pond.

Question 4

Define interspecific competition:

Answer 4

• Occurs between individuals of different species where the niches in a habitat are VERY SIMILAR e.g. tadpoles and small fish for food in a pond.

Complete Learning Activity 9 - Page 12 of your textbook.

Question 5

NB: Define ecological niche:

Answer 5

All the conditions necessary for an organism to survive and **reproduce. **

Question 6

List the requiements that form the the ecological niche of the individuals:

Answer 6

1. Tolerate the physical environment (temperature,pH)
2. Obtain energy and nutrients
3. Cope with competition
4. Avoid predators

Question 7

What happens when two species with the same or similar ecological niches occupy the same habitat?

Answer 7

• **Their ecological niches will overlap. **
• This can result in specialisation amont closely related species e.g.
• Galapagos finches - evolved a large variety of beak shapes and sizes to suit their own type of food, creating their own ecological niches to prevent competition. (See later page 247)
• The competition that arises from overlapping ecological niches can also lead to **two possible outcomes: **
  1. * Competitive exclusion or
  1. * competitive co-existence.

Question 8

Define specialisation:

Answer 8

The **structural **and behavioural adaptations that enable individuals of different species to co-exist.

Question 9

Explain competitive exclusion:

Answer 9

• When one of the two competing species is much more sucessful than the other. The succesful species survives and the other **disappears. **
• Can lead to extinction.
• Can play NB **role in evolution. **
• E.g. monkeys out-competed lemurs in Africa. Only found in Madagascar.

Question 10

Explain competitive co-existence:

Answer 10

• Arises when two competing species co-exist in the same habitat.**
• Despite overlapping niches, and therefore competition for the same resources, they are able to co-exist because they use the resources DIFFERENTLY.
• RESOURCE PARTITIONING

Question 11

Define resource partitioning:

Answer 11

The evolutionary process whereby
species with similar requirements,
living in the SAME HABITAT,
evolve specialised TRAITS that enable them to utilise the resources differently,
creating seperate niches to reduce INTERSPECIFIC competition and make CO-EXISTENCE possible.
This leads to greater **diversity **of species on earth.

Question 12

How can resources be partitioned?

Answer 12

Two species can eliminate competition for the SAME resources by using the resources:
1. At different times - e.g. mouse feeds on insects during day, second species at night.
1. In different parts of habitat - e.g. different species of fish feeding on same resource but at different depths in a lake
1. In different parts of the same plant - e.g. giraffe feedings on upper leaves, kudu on lower leaves.

Question 13

Discuss how plants in a forest may use resource partitioning:

Answer 13

• Plants in an indigenous forest may compete for light.
• The intensity of light diminishes as the rays pass throught different layers of forest vegetation.
• Different species of plants have created different niches by STRATIFICATION.
• The different layers of vegetation are ADAPTED to photosynthesise in different light intensities.
• I.e. resource, namely LIGHT, is partitioned.

How clever?!

Question 14

Define STRATIFICATION:

Answer 14

• Indigenous forests are complex communities made up of **many different trees and plants, varying in size and species. **
• This creates a vertical structurethat divides vegetation into layers.
• This pattern is called **STRATIFICATION. **
• The conditions at the uppermost layer is **quite different **to the lower layers e.g. LIGHT, WIND SPEED, HUMIDITY

Question 15

What are the layers that a forest ecosystem is made up of:

Answer 15

1. Tall trees - higher up canopy
2. Shorter trees - understory of a forest
3. Pioneer species and young trees - grows in gaps between trees
4. Epiphytes (lichens, mistletoe, orchids) and climbers (cat-thorn, forest grape) that twine around branches

Question 16

Strategies amongst animals - discuss how large herbivores co-exist in the African savannah: Give and example.

Answer 16

Both giraffe and kudu are browsers

Giraffe - long neck and legas - body adapted to reach higher branches of trees.
Giraffe feed on many species e.g. acacia tortillis (umbrella acacia). Tough tounge and lips - can withstand vicious thorns. They obtain food beyond the reach of other hoofed animals in same habitat.

Kudu - purely browsers, not known to eat grass. Utilse a wider range of trees than any other antelope. Prefer young shoots and leaves but will also eat seedpods of trees sur as Terminalia species.

• Share many preferred species with Giraffe, such as bush willow, but competition eliminated due to HIGHT of where the browsing takes place. HIgher v Lower branches utilised for browsing.

Question 17

What strategies are utilised by co-existing mixed communities of shorebirds? Discuss.

Answer 17

• Differences in feeding habits
• Differrences in morphology

Question 18

D

Discuss the strategies that are utilised by co-existing mixed communities of shorebirds relating to FEEDING HABITS:

Answer 18

Although huge flocks of different shorebirds - they practice RESOURCE PARTITIONING by dividing up the territory both horizontally and vertically:

Horizontal division = differernt species may feed: above the tide line, follow the waterline of waves, in the shallows, on rocky outcrops, in deeper water (the ones with longer legs)

Vertical division = pick titbits of the ground, probe underground, prey on creatures living deeper in water, feed on tidbits floating on the water surface

Question 19

Explain how shorebirds are divided into **pickers **and probers, and the relevance of this division:

Answer 19

**PICKERS: **Search for food by sight and forage in a typical run-and-peck manner. They run a certain distance with their head high then stop abruptly and peck at a morsel of food. E.g. White-fronted sandplover

PROBERS: Have long bills and they stick these in soft mud or sand to feel for prey e.g. Sandpiper’s bill tip is mobile ad can act as a finger tip to grasp or grip prey of insect larvae or worms

Question 20

What morphological adaptations have shorebirds made? Give examples

Answer 20

Different length bills and legs - enable them to feed on different types of food:

• **Triangular bill **of Oystercatcher = cross between knife and chisel. Stab and severr muscles, smash open shells
• **Upturned bill **e.g. Avocet = scythe the water, sweeping back and forth to stir up and snag prey
• Long, slender legs of Waders = wading into water to feed on molluscs, crustaceans and small fish.

Question 21

Both leopard and lion are skilled hunters - they are opportunistic, stalk their prey an co-exist because of resource partitioning. Discuss the strategies of coexisting predators e.g. lions and leopards:

Answer 21

• Hunting at different times of the day = leopards mainly nocturnal, will hunt during day when camouflaged by dense foliage. Lions tend to hund in early morning or at night.
• Hunting different types of prey = e.g. lion prey mainly on medium sized mammals e.g. wildebeest, zebras, warthogs v Leopards that prey on smaller prey such as antelope (like impala) and smaller monkeys.
  Example of **DIETARY NICHE seperation. **
• **Hunting different areas of habitat **= lions are larger and heavier than leopards, which they tend to dominate. Leopards are faster than lions more able to subsist on smaller prey. Also can climb trees - keeping prey safe from lions. (Lions can climb trees, but not to the extent of the leopards)

Look at learning activity 10 page 16 of the textbook.