Chap 13 - CRCBiologyY11
Transcript Chap 13 - CRCBiologyY11
Area of Study 2
Chapter 13 – Ecosystems and their living
Identify the components of an ecosystem
Understand the nature of a living community
Become aware of the various ecological roles in a community
Understand the variety of interactions that occur within an
A community is all the different species living together in the one
habitat. Each community is made up of populations living at the
same location at the same time.
All the different populations living at one location at a particular time
form a community:
community 1 = pop 1 + pop 2 + pop 3 ... so on
Communities in different ecosystems can vary in their diversity.
Diversity is not simply a measure of the number of different
populations (or different species) present in a community.
When ecologists measure the diversity of a community, they
consider two factors:
The richness or the number of different species present in the
sample of the community, and
The evenness or the relative abundance of the different
species in the sample
As richness and evenness increase, the diversity of a community
Each population consists of one species that may be a different species
of animal, plant, fungus, protist or microbe.
A population is defined as all the individuals of one particular species
living in the same area at the same time.
An ecosystem consists of a community, its physical surrounding, and
the interactions between and within them. The study of ecosystems
is the science known as ecology.
Each ecosystem includes a living part and a non-living part. The living
(biotic) part is a community that consists of the populations of
various species that live in a given region.The non-living (abiotic)
part consists of the physical surroundings.
Ecosystems can vary in size, but must be large enough to allow for the
interactions that are necessary to maintain them.
An ecosystem may be as small as a freshwater pond or a terrain as large
as an extensive area of mulga scrubland in inland Australia.
Ecosystems are generally named on the basis of the dominant
E.g. ‘an open grassland ecosystem’
‘tall closed forest ecosystem
or naming can be more specific
E.g. ‘a tall open Eucalyptus forest ecosystem’
If we look at a variety of ecosystems, we find that the living community
in each ecosystem differs. The various populations that make up each
community have physical, biochemical and behavioral features that
equip them for survival and reproduction in the particular
environmental conditions of their ecosystem.
Read pages 411-414
‘The community of a littoral zone’
‘The community of an open forest’
‘The community of a Mallee ecosystem’
Construct a table which outlines the major featues of the
environment and outline the physical, biochemical and
behavioral features of the fauna that equip them for survival and
reproduction in the particular environmental conditions of their
Ecological groupings within an
The living community of different ecosystems, re apparently very
different in terms of the species that are present. However, there
is a common pattern to each community.
Members of every community can be identified as belonging to one
of the following ecological groups: producers or autotrophs;
consumers or heterotrophs; decomposers
Producers - Autotrophs
The community in every functioning ecosystem must contain some
species that can be identified as producers or autotrophs.
Producers or autotrophs are the members of the community that can
manufacture their own organic compounds, such as glucose, from
simple inorganic compounds, such as carbon dioxide, using an
abiotic source such as sunlight.
Producers - Autotrophs
This chemical energy is them made available, either directly or
indirectly to all other members of the living community of that
The process by which most producers transform the radiant energy
of sunlight into the chemical energy of sugars is known as
carbon dioxide + water
glucose + oxygen
Producers - Autotrophs
In aquatic ecosystems, such as seas, lakes and rivers, the producers are
microscopic phytoplankton, microscopic algae and seagrasses.
In terrestrial ecosystems the producers include trees, grasses and other
flowering plants, cone bearing plants (e.g. pines), and other kinds of
plants such a ferns and mosses.
Consumers - Heterotrophs
Consumers or heterotrophs are those members of a community that
must obtain their energy by eating other organisms or parts of them.
All animals are consumers!
Consumer organisms can be subdivided into the following groups:
- herbivores that eat plants (wallabies and koalas)
- carnivores that eat animas (numbats and snakes)
- omnivores that eat both plants and animals (humans and bears)
- detritivores that eat decomposing organic matter such as rotting
leaves, dung or decaying animal remains.
Consumers - Heterotrophs
Particles of organic matter are called detritus. Detritus is made up
of dead leaves, animal remains, animal faeces etc, in short, all
organic matter that contains chemical energy.
Detritivores are animals that eat detritus.
They differ from decomposers as they release enzymes onto the
detritus, partially breaking it down, and then they absorb some
of the products.
Typical decomposer species in a community are various species of fungi
Decomposers are heterotrophs that obtain their energy and organic
matter and in this case, the ‘food’ is dead organic material.
Decomposers differ from other consumers because as they feed, they
break down organic matter into simple inorganic forms or mineral
nutrients, such as nitrate and phosphate.
So, decomposers are extremely important to the environment as they
convert organic compounds to inorganic compounds which the
They are also important as they break down the wastes or consumers,
so that they don’t build up.
This is the cycling of matter in an ecosystem.
Interactions within an ecosystem
In ecosystems, interactions are continually occurring:
between the living community and its abiotic surroundings
within the abiotic surroundings
within the living community
Organisms and their surroundings
Refer to figure 13.18 p419
List the interactions between the environment and:
The Tasmanian devil
Within abiotic surroundings
Use the example of a storm to show the effects that some abiotic
factors have on other abiotic factors within an environment
Interactions within a living community
Symbiosis is the term we use to describe when different species live
together in a relationship.
The relationships can be classified as:
Competition occurs when organisms living in a community are
competing for the same resources.
Competition may occur between:
members of the same species – intra-specific competition
members of different species – inter-specific competition
Read p421-422 and explain how some strategies animals use to combat
Where one species, the predator, kills and eats another animals species,
Prey species have adapted strategies to help them avoid being caught:
Structural features – camouflage, mimicry.
Behavioral features – keeping still, having a sentry (lookout),
Biochemical features – produce repellant or toxins (often signaled by
Herbivores obtain their nutrients from eating plants.
But plants do not want to be eaten…
so what can they do?
To deter predators, plants can produce:
- spines, spikes or thorns
- chemicals, toxins or poisons
To deter other plants from growing in their space:
chemicals to inhibit the growth of other plants in the area
Where one species, the parasite, feeds and lives off the other species,
Exoparasites live on the exterior of the body e.g. fleas, ticks.
Endoparasites live inside the body e.g. intestinal or heart worms.
In parasitism, the parasite harms the host in some way, but does not
generally kill it.
In plants, there are two main types of parasite-host relationships:
halo-parasitism – the parasite is totally dependant on the plant for
all its nutrients (very rare e.g. Genus Rafflesia)
hemi-parasitism – the parasite obtains some nutrients from the
host, but can also make its own food (e.g. mistletoe species)
A relationship involving two different species where both species
benefit from the relationship.
Provide two examples.
A relationship where one animal benefits from the relationship, and
the other neither benefits nor suffers.
Provide one example.
Minimising competition between species
Organisms need to not be in direct competition with each other for
every resource they require.
When various species in the same community differ in the use that
they make of a resource, such as food or space, the various species
are said to show niche separation.
The greater the niche separation between the two species, the smaller
the level of competition between them.
If however, two species use the same resource in similar ways, they
can be said to show niche overlap.
The greater the niche overlap, the greater the intensity of
competition between the two species.
Answer the following ‘quick-check’ questions:
Questions 1 & 2 – Page 411
Questions 3 & 4 – Page 419
Questions 5 & 6 - Page 433.
Biochallenge – Page 434
Chapter Review Questions – 2, 4, 5 and 7