Download Succession and Change in the Ecosystem

Science 7: Unit A – Interactions and Ecosystems – Topic 6:
Succession and Change in the Ecosystem
I.
Succession
 Succession occurs when changes in an ecosystem lead to some
species replace other species in the ecosystem.
 Eg. A fire burns through a forest, destroying trees and grass. A
few years later, scrubs and bushes are growing in the same
location.
 ___________ ___________ is the gradual growth of organisms
in an area where no life previously existed.
 Lichens, moss, and ferns are usually the first organisms to grow
on bare rock.
 As these organisms do establish themselves, the break down
rock and make the ecosystem more suitable for other, more
complex species of life.
 _____________ _____________ is the gradual growth of
organisms in an area that already hosted life.
 The example of the forest fire is an example of secondary
succession.
 Some species of bushes grow best in soil where there are large
amounts of ash.
 Because humans are having a wide effect on many ecosystems,
we are influencing the process of succession in these
ecosystems.
 Certain species of animals succeed in an ecosystem because
they can adapt to the changes we cause in an ecosystem. These
species are called generalists because they are a jack-of-all
trades that scavenge for scraps of food we leave behind.
II.
Generalists Are Growing in Numbers.
 Generalists are species that can __________ to wide range of
conditions. They include: rats, raccoons, cockroaches, seagulls,
pigeons. Many generalists are ______________.
 These animals are succeeding against native animals such as
owls, wolves, foxes, etc. Many of the animals suffering are
carnivores and herbivores. These animals cannot adapt as easily
to living with humans.
III. Pest Control
 Using chemicals such as DDT to kill pests leads to quite a few
problems. Pollution, resistance, and bioaccumulation.
 When you use a pesticide it can affect organisms that you don’t
want to harm, such as your crops.
 Also, using pesticides can lead to the pest species developing
____________ to the chemical.
 _____________ ______________ - Is another way to
eliminate pests is to use their predators as a natural pesticide.
 Beetles and lady-bugs are very effective at controlling pest
plants and animals.
 There is still a risk with biological control. Introducing species
into a new area could have unpredicted effects.
 An ______________ _____________ is one that is brought to a
new ecosystem with humans. Often introduced species do
damage to the ecosystem by harming the organisms there.
 Eg. Settlers brought rabbits with them to Australia. The rabbits
escaped into the wild, and without predators in Australia, began
to grow quickly in numbers, feasting on the grasses. This lead to
a drop in the herbivore population in that part of Australia.
IV.
Extinction, Extirpation, Endangered, and Threatened
Species
 ______________ ______________ – a species whose numbers
are dropping.
 _____________ ______________ – a species whose numbers
are so low that they are in danger of becoming extinct or
extirpated in an area.
 ______________ - a species which has been completely wiped
out .
 ______________ – a species which has been wiped out in an
area or ecosystem.
 Humans have had a large impact on recent extinctions. This
happens in a numbers of ways:
 1. Loss of _______________________________. If the
organism loses its home, everything else will suffer.
 2. ___________________ by humans.
 3. _____________ from introduced species. An introduced
species can eat all of the species’ food, or the species itself.
 By designating certain areas as ____________
_____________. Wildlife preserves are areas that we leave
completely alone. They are not parks because people are not
even supposed to go camping there.
 Habitats are preserved and introduced species are kept from
spreading into the preserve.