Unit A

1
Unit A Biological Diversity

• Topic 2 Habitat and Lifestyle

2
Variation and Adaptation

• The goal of life is to survive long enough to
  reproduce and pass on your genes. (R. Dawkins).
• Adaptations allow organisms to have a higher
  chance of survival and reproduction.
• The more variations in a species the better the
  chance that adaptations will arise, causing the
  species to survive and thrive.
• Variations can allow living things to live in
  very harsh conditions, from the Arctic to the
  Sahara to maybe Mars itself?

3
Competition

• Because resources such as mates, food, shelter,
  etc. are scarce, species and organisms in the
  same species must compete for them.
• Competition allows the best species and organisms
  to survive and pass on their genes improving the
  gene pool of the species.

4
Avoiding Competition

• Some species are better than other species at
  certain activities, so it doesnt make sense for
  the weaker species to compete. Instead they
  assume a different niche in the ecosystem. This
  increases the variation between species.
• Eg. Lions are stronger and better hunters than
  hyenas, so the hyenas evolved into scavengers,
  eating the scraps left behind by the lions.

5
Broad Niches

• Broad niches exist in areas that are harsh on
  organisms such as the Arctic and desert.
• Species that live in broad niches must make the
  best of the available situation. They must become
  generalists or perish.
• Generalists are species that can adapt to
  different situations eating a variety prey,
  living in different shelters.

6
Broad niches Contd

• Broad niches can only support a few different
  kinds of generalists as resources are very
  limited.
• Because species are few, the population sizes can
  become very large as they are very good at
  adapting to different conditions.

7
Specific Niches and Specialists

• As conditions improve near the equator, the
  conditions become hospitable to life and a wide
  variety niches are available allowing for a wide
  variety of species.
• In the rain forests, each species can survive in
  a tiny area (specialists), therefore there are
  millions of species with very small population
  sizes as competition is much greater.

8
The Trend for the Future

• As humans spread their influence throughout the
  world, resources and niches are becoming scarcer
  for living things.
• These conditions are favourable to generalists,
  and harmful to specialists. Superb generalists
  such as rats, black bears, and cockroaches are
  increasing in numbers.

9
Trend for the Future Contd

• Specialists species such as tigers, eagles, and
  whales are now endangered or threatened species.
• A specialist depends on having its small,
  specialized niche, but these niches are much more
  fragile than broad niches and so its easy for
  them to go extinct.

10
Symbiosis

• Symbiosis a relationship between two organisms
  where at least one of them benefits. There are
  three kinds of symbiotic relationships.
• Parasite is the organism which attaches onto
  the larger host and lives off them in some way.
  They are usually smaller than the host.
• Host is the organism which can exist without
  the other. The parasite needs the host more than
  the host needs the parasite. Theyre also usually
  bigger than the parasite.

11
I. Commensalism

• A symbiotic relationship the parasite benefits,
  and the host organism is not affected either way
  (neutral).
• The Remora fish benefits from hanging around
  sharks, eating its scraps, while the shark is not
  affected.

12
II. Mutualism

• A symbiotic relationship where both the parasite
  and host benefit.
• Certain species of birds live on the back of
  large mammals such as hippopotamuses and eat the
  insects and pests which bite and irritate the
  hippo, therefore both benefit.

13
III. Parasitism

• This is a symbiotic relationship where the
  parasite benefits, but the host suffers.
• An example of a parasitic relationship would be
  lice and humans, or bedbugs and humans, or fleas
  on dogs.