Transcript Unit A – Biological Diversity

Unit A – Biological Diversity
Topic 2: Habitat and Lifestyle
Variation and Adaptation
• The goal of life is to survive long enough to
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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?
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.
Avoiding Competition
• Some species are better than other
species at certain activities, so it doesn’t
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.
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.
Broad niches Cont’d
• 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.
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.
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.
Trend for the Future Cont’d
• 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.
Symbiosis
• Symbiosis – a relationship between two
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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. They’re also
usually bigger than the parasite.
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.
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.
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.