V.C.E. Biology Unit 2

Area of Study 2Dynamic Ecosystems

Chapter 13 – Ecosystems and their living environment

Key Knowledge 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 ecosystem

Community

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.

Diversity

When ecologists measure the diversity of a community, they consider two factors:

1. The richness or the number of different species present in the sample of the community, and

2. The evenness or the relative abundance of the different species in the sample

As richness and evenness increase, the diversity of a community also increases.

Populations

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.

EcosystemsAn 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.

Naming ecosystemsEcosystems are generally named on the basis of the

dominant vegetation. E.g. ‘an open grassland ecosystem’

‘tall closed forest ecosystem

or naming can be more specific

E.g. ‘a tall open Eucalyptus forest ecosystem’

Ecological communities

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.

Ecological communities

Your TaskRead 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

ecosystem.

Ecological groupings within an ecosystem

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 ecosystem.The process by which most producers transform

the radiant energy of sunlight into the chemical energy of sugars is known as photosynthesis:

light energy

carbon dioxide + water glucose + oxygen

(LOW ENERGY) (HIGH ENERGY)

Producers - AutotrophsIn 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.

DecomposersTypical decomposer species in a community are

various species of fungi and bacteria.

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.

DecomposersSo, decomposers are extremely important to the environment as they convert organic compounds to

inorganic compounds which the producers need.

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:a) The Tasmanian devil

b) The Daffodil

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

Competition Predator-prey relationships

Parasitism Mutualism

Commensalism

Symbiosis Symbiosis is the term we use to describe when

different species live together in a relationship.

The relationships can be classified as:- parasite-host

- mutualism- commensalism

Competition

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 competition.

Predator-prey relationships

Where one species, the predator, kills and eats another animals species, the prey.

Prey species have adapted strategies to help them avoid being caught:

Structural features – camouflage, mimicry.

Behavioral features – keeping still, having a sentry (lookout), schooling

Biochemical features – produce repellant or toxins (often signaled by bright colouration)

Herbivore-plant relatonships

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

Parasite-host relationships

Where one species, the parasite, feeds and lives off the other species, the host.

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.

Why?

Parasite-host relationships In plants, there are two main types of parasite-host

relationships:

1) halo-parasitism – the parasite is totally dependant on the plant for all its nutrients (very rare e.g.

Genus Rafflesia)

2) hemi-parasitism – the parasite obtains some nutrients from the host, but can also make its own

food (e.g. mistletoe species)

Mutualism A relationship involving two different species where

both species benefit from the relationship.Provide two examples.

Commensalism

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.

Questions Answer the following ‘quick-check’ questions:

Questions 1 & 2 – Page 411Questions 3 & 4 – Page 419 Questions 5 & 6 - Page 433.

Biochallenge – Page 434

Chapter Review Questions – 2, 4, 5 and 7