Transcript Biodiversity - GaryTurnerScience

Biodiversity refers to the number of different
species present in a community.
Biodiversity
 Biodiversity refers to the
number of different species
present in a community.
 Communities with high
biodiversity survive
environmental change well.
 If something destroys one of
the organisms in the food
chain then the other
organisms simply switch to
different food sources.
Biodiversity
 Communities with low biodiversity
have little or no ability to switch to
other food sources and may die off
as a result of change in the
environment.
 If the herbivore animals in a
community eat only one particular
plant species, then they will die out
if that plant species is destroyed by a
disease or some other disaster.
 The carnivores that eat the
herbivores would die out too. If the
herbivores had a variety of plants to
choose from they would probably
survive the loss of one particular
species.
Biodiversity
 Humans have reduced the
biodiversity of many
ecosystems.
 Natural vegetation has
been removed and
replaced by crops or forests
of only one plant species.
 As a result, many species
are now endangered or
extinct.
 Pine plantations and fields
of wheat and sugarcane,
for example, have very low
biodiversity.
Relationships between organisms
 Organisms do not live by
themselves but interact
with the other organisms
in the ecosystem.
 Some interactions
benefit both organisms
while other interactions
benefit one organism
while harming the other.
Benefiting both organisms
 Mutualism (symbiosis) is
when both organisms benefit
from their relationship with
each other.
 For example, some sharks
have their mouths nibbled by
small fish. The fish get an
easy meal and the sharks get
their teeth scrubbed clean.
 Bees collect pollen for their
hive, but they also spread it to
other plants allowing their
reproduction.
Symbiosis (mutualism)
 Clownfish have a mucous
coating that allows them to live
among these poisonous
tentacles without being stung.
 Clownfish receive protection
from predators and feed on the
anemone’s leftovers.
 In return the anemone gets
cleaned. This is an example of
symbiosis or mutualism.
 Sea anemones are animals. Their
tentacles contain stinging cells
with which they stun passing
fish and then drag their prey
towards their mouth.
Hitching a ride
 Sea anemones sometimes
hitch a ride on the back of
hermit crabs.
 The hermit crab is
camouflaged and
protected by the anemone,
and the anemone gains
mobility.
 Both benefit from the
relationship.
Benefiting one organism
 Commensalism is when one
species benefits while the
other species is unaffected.
 Remora are tropical fish that
attach themselves to fasterswimming fish such as
sharks.
 The sharks are not harmed by
their presence but do not
benefit from it either.
 The remora benefit in two
ways: they get a free ride and
they consume any of the
shark’s ‘leftovers’.
Harming one organism
 Amensalism is when one species is harmed while the
other species is unaffected.
 Trails caused by cows and sheep throughout feeding
areas may not affect the animals, but the plants they
walk on are destroyed.
No benefit at all
 Competition is when animals compete for food, water
or nesting materials.
 Plants compete for nutrients, water, and light. Weeds
in the garden often crowd out other plants.
 They grow so quickly that other plants suffer and die.
BENEFITING ONE ORGANISM,
HARMING ANOTHER
 Exploitation is when one species benefits from the interaction while
the other is harmed.

 • Predation: where one animal kills another for food. A seal catching a
fish or a perentie lizard snatching a wallaby are examples of predation.

 • Herbivory: where a herbivore eats a plant, reducing it in size but not
killing it. This happens when kangaroos graze on grass, possums eat
bottlebrushes or when dugongs feed on sea grasses.

 • Parasitism: where one organism (the parasite) lives on or in another
(the host). The host is usually not killed but is robbed of its nutrients,
making it ill. Tapeworms are parasites that live in the gut of animals.
Dogs and cats often have tapeworms if not treated. Humans sometimes
have parasites such as head lice and threadworms.
Eating from the inside out
 Parasitoids are parasites
that kill their hosts. An
example of a parasitoid is
the braconid wasp,
which lays its eggs inside
the cabbage caterpillar.
 When the eggs hatch,
the wasp grubs eat the
caterpillar from the
inside out!