ecosystems

Can they be considered ecosystems?

Prof. Ignacio Álvarez Calleja

What is an ecosystem?An ecosystem is formed by a set of living beings, the physical environment where they live and the relationships between them. Thus, ecosystems have two components:

– Biocenosis (living component) – Biotope (non living component)


Biotope

• It is made up of the environmental conditions such as air composition, type of soil, water, temperature, mineral salts, humidity, light, salinity …

• It refers to a particular place or geographical area where the biocenosis lives.


Biocenosis• It is made up of all the living beings that

live in the ecosystem.• We can distinguish 3 levels:

– Organisms– Populations– Biological communities


There are 2 types of factors that affect living beings in an ecosystem:

– Biotic factors are the effects which living beings have on other organisms (competition, predation, reproduction . . .)

– Abiotic factors are the physical and chemical elements in an ecosystem that affect living beings (temperature, humidity, salinity . . .)


Distribution of organisms in Ecosystems

Which type of factor do you think is most responsible for the distribution of organisms in ecosystems? Biotic or abiotic?

Would these factors be the same for terrestrial and aquatic ecosystems?


TERRESTRIAL ECOSYSTEMS• Temperature

• Light

• Humidity


AQUATIC ECOSYSTEMS• Light

• Temperature

• Oxygen

• Pressure

• SalinityProf. Ignacio Álvarez Calleja

TROPHIC RELATIONSHIPS

In an ecosystem, seveal interactions take place between the different organisms in terms of who eats who.

These are called trophic relationships.


• Producers - organisms which can make their own organic matter (plants, algae, some bacteria)

• Consumers – organisms that consume already made organic matter (they can be herbivores, carnivores or omnivores).

• Decomposers – organisms which feed on dead organic matter from the environment (fungi, bacteria and some animals like earthworms).

Depending on their source of food, living beings can be classified into

3 groups:


What is a food chain?• Food chains show which organisms

eat other organisms

Grass Rabbit Fox

• The arrows show the transfer of matter and energy from one organism to the next.


• Each level of a food chain is known as a trophic level.

• Food chains always start with a producer. Producers are always on the first trophic level.

• Consumers can be classified as primary, secondary, tertiary, top predators and scavengers.


Food Chains

Oak Tree

Beetle

Wood mouse

Owl

Producer

Primary consumer

Secondary consumer

Tertiary consumer

First trophic level

Second trophic level

Third trophic level

Fourth trophic level

Each level of a food chain is known as a trophic level


• The first one is a food chain.• The second one is a food web.• Soooooooo…..what do you think is the

difference between the two of them?mmmmmmmm? What?


Questions

1. What will happen to the number of clown fish if the sharks become vegetarian?

2. What effect will this have on the number of zooplankton?

3. What will happen to the Blue Regal fish if a disease wipes out the small invertebrates.

Great White Shark

Clown Fish Sea Turtle

Algae

Blue Regal

Zooplankton

Small Invertebrates

Food Web


Food chains and food webs• A food web consists of all the

interconnected food chains found in an ecosystem. Thus, a food web gives more information about the ecosystem than a food chain.


SOMETIMES A SMALL CHANGE . . .

…HAS BIG CONSEQUENCES.Prof. Ignacio Álvarez Calleja

Trophic pyramidsA trophic pyramid is a representation of a characteristic of the trophic levels of an ecosystem. There are different kinds of trophic pyramids:

- Number pyramid

- Biomass pyramid

- Energy pyramid


In ecosystems matter and energy are transmitted through the food relationships between organisms.


So we could say that there are two processes

occurring at once: a one way flow of energy and a closed cycle of matter.


ecosystems

Environment