Animal Ecology ZLY 311 Ecosystem Biosphere portion of

Animal Ecology (ZLY 311)

Ecosystem • Biosphere - portion of the earth which sustains life • very huge & can not be studied as a single entity • divided into distinct functional units • Ecosystem Definition 1 – communities of organisms live together – interact with each other – Interact with their physical environment Definition 2 – functional unit of nature – encompassing complex interaction between living and abiotic components

Main Ecosystems: • • Desert Rainforest Ocean Taiga Tundra Chaparral Grassland Temperate Forrest

Components

• 3 groups 1. Physical factors: – Sun light, temperature, rainfall, humidity and pressure. – sustain and limit the growth of organisms in an ecosystem 2. Inorganic substances: – CO 2, N 2, O 2, P, S, H 2 O, rock, soil and other minerals 3. Organic compounds: – Carbohydrates, proteins, lipids and humic substances. – building blocks of living systems – make a link between the biotic and abiotic components. Abiotic components Nonliving

• 3 groups Biotic components – 1. Producers: autotrophs Living – green plant manufacture food for the entire ecosystem - photosynthesis – water and nutrients from the soil – carbon dioxide from the air – solar energy 2. Consumers: heterotrophs – consume food synthesized by the autotrophs – three groups • Herbivores feed directly on plants • carnivores eat other animals • omnivores feeding upon both plants and animals

Biotic components – Living. Decomposers: saprotrophs – Mostly bacteria and fungi – feed on dead – Feed on decomposed – Feed on organic matter – secrete enzymes outside their body on the decaying matter – recycling of nutrients – detrivores or detritus feeders

Types of ecosystems • Two main types • Natural ecosystems – Totally dependent on solar radiation e. g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines. – Ecosystems dependent on solar radiation and energy subsidies (alternative sources) such as wind, rain and tides. e. g tropical rain forests, tidal estuaries and coral reefs. • Man made ecosystems – Dependent on solar energy-e. g. Agricultural fields and aquaculture ponds. – Dependent on fossil fuel e. g. urban and industrial ecosystems.

Pond as an example • • complete, closed an independent ecosystem convenient to study its basic structure and functions works on solar energy maintains its biotic community in equilibrium

Abiotic components in a pond ecosystem • Light – Solar radiation provides energy that controls the entire system – Penetration depends on transparency of water, • amount of dissolved or suspended particles • number of plankton – On the basis of extent of penetration of light a pond can be divided into 3 zones 1. Euphotic (eu=true, photic=light) - Plenty of light available 2. Mesophotic 3. Aphotic No light is available in the aphotic zone Pigure of the layers of lake Secchi disc

Abiotic components in a pond ecosystem • Inorganic substances – Appear in two forms 1. Dissolved form • O 2 and CO 2 2. Reserved form • nitrogen, phosphorus, sulphur and other inorganic salts • In bottom sediments • inside the living organisms • A small fraction found dissolved – Water • plants and animals depend on water food and exchange of gases

Abiotic components in a pond ecosystem • Organic compounds – amino acids and humic acids – breakdown products of dead animals and plants – Found in dissolved form or suspended in water

Biotic components of a pond ecosystem • 3 groups 1. Producers or autotrophs • synthesize food • groups – Phytoplankton – Rooted plants – Rooted submerged – Rooted emergent – Floating plants 2. Consumers/Heterotroph 3. Decomposers

1. Producers or autotrophs • phytoplankton – Floating microorganisms – Bloom – Spirogyra, Ulothrix, Cladophora, Diatoms, Volvox.

• Rooted plants – concentric zones from periphery to the deeper layers – Three distinct zones i. emergent vegetation: . eg. Typha, Bulrushes and Sagittaria ii. rooted vegetation with floating leaves. eg. Nymphaea iii. submergent vegetation: eg. Hydrilla

2. Consumers/Heterotrophs in a pond • animals feed directly or indirectly on autotrophs • classified in to 3 groups • Zooplankton, Nectons, benthic animals – Zooplankton • floating animals - Cyclops, Cypris Cyclops

2. Consumers/Heterotrophs in a pond – Nektons • can swim and navigate at will - fishes, tadpoles

2. Consumers/Heterotrophs in a pond – Benthic animals • bottom dwellers: beetle, mites, mollusks and some crustaceans.

3. Decomposers in a pond ecosystem • distributed through out the pond • Abundant in the sediment • bacteria and fungi • Rhizopus, Penicillium, Curvularia , Cladosporium