The strongest competition for survival is
between members of the same species.
Solitary animals avoid each other, so
that competition is at a minimum. The
animals that live in groups must strike a
balance between the benefits of sticking
together, and the increased competition
for food and mates. Social groups range
from simple ones that provide safety in
numbers, to complex societies, where
members hunt together and protect
each other’s young.
The most highly social animals are
ants, wasps, and bees. They are eusocial,
which means there is division of labour,
with different members of the colony
performing specific jobs for the good
of the whole. The colony works for
their mother, the queen, to raise huge
numbers of yet more sisters. All work
is done by females. Only a few males
are produced every year to mate
with the next generation of queens.
When animals of two species cooperate with each other,
the relationship is known as symbiosis. There are two types.
In mutualistic relationships, both partners benefit from the
actions of the other. Commensal relationships are rarer.
They involve one animal benefiting from the association,
while the other receives no benefit, but is not harmed either.
A parasite is an organism that lives on
or inside another, known as the host.
The parasite either eats the body of the
host or consumes some of its food. The
host is disadvantaged by the relationship,
but is not killed—if it was, the parasite
would soon die as well in many cases.
A parasitoid is an animal that does kill
its host, generally as a larva eating
it alive. Once the host is dead, the
parasitoid takes on an independent
mode of life (see page 91).