Advanced Higher Biology Unit 2 Environmental Biology Section
Advanced Higher Biology Unit 2 Environmental Biology
Section A- Circulation in Ecosystems 1. 2. 1 Energy Flow
Reminder 100% solar radiation 36% reflected from atmosphere 64% entering atmosphere reflected or absorbed, used then re-emitted as heat
Extra Note The Laws of Thermodynamics and Matter Transformations • Energy cannot be created or destroyed – only be transformed from one kind to another • Disorder in the universe is increasing – During transformation the resulting energy is less organised and less useful. – The final transformation is usually into heat
Energy Flow In Ecosystems • Energy is not recycled. • Movement of energy is through a system. • From an external source (the sun). • Through a series of organisms and back to the environment. • Leaves as degraded energy (heat).
Energy Availability • 1% of the energy reaching the earth from the Sun is available to life on Earth. • Of this energy, 3% (0. 03% of the total) is trapped by green plants or algae. (autotrophs) • All life on Earth is comes from 0. 03% of the energy absorbed from the Sun.
What are Food Chains? • Groups of animals and plants that are linked together by what they eat. • Food chains exist to pass energy from one organism to the next!
A Food Chain Carnivore Quaternary Consumer Carnivore Tertiary Consumer Carnivore Secondary Consumer Herbivore Primary Consumer Energy Flow Plant Producer
Food Chains and Trophic Levels • The stages in food chains are called trophic levels. • Each trophic level depends on energy. • Energy is passed up the trophic levels • All life above the first trophic level gets its energy by consuming the one below.
Trophic Levels The third trophic level belongs to carnivores or second order consumers. The second trophic level belongs to herbivores or first order consumers. The first trophic level belongs to producers or plants
Trophic Structure • Trophic Structure – The organization of feeding levels in an ecosystem • Species in an ecosystem are divided into trophic levels on the basis of their main source of nutrition.
Terrestrial Food Chain Carnivore Herbivore Plant 5 th Trophic Level (Quaternary Consumer) 4 th Trophic Level (Tertiary Consumer) 3 rd Trophic Level Trophic (Secondary Consumer) Structure 2 nd Trophic Level (Primary Consumer) 1 st Trophic Level (Producer)
Marine Food Chain Carnivore Quaternary Consumer (5 th Trophic Level) Carnivore Tertiary Consumer (4 th Trophic Level) Carnivore Secondary Consumer Trophic (3 rd Trophic Level) Structure Zooplankton Primary Consumer 2 nd Trophic Level Producer Phytoplankton (1 st Trophic Level)
Trophic levels • Layers in ecosystem • Through which energy flows • referred to as trophic (feeding) levels • Energy lost at each trophic level • Much energy lost as • Metabolic heat
Energy and Trophic Levels • Only about 10% of the energy from one trophic level can get to the next. • The rest of the energy is lost as heat.
Energy loss as heat in food chains
Energy At Trophic Levels Energy Usage Energy flows through the system and is not recycled Faeces Cellular Respiration (to decomposers) ( lost as heat) Growth (to next trophic level)
Trophic Levels • Animals feeding wholly on plants occupy a single trophic level • But most animals at higher trophic levels occupy several trophic levels simultaneously because of variation in their diets.
A Simplistic Approach • In practice food chains do not exist in isolation. • Would lead to instability in populations. • Food chains are normally interlinked to form food webs.
Food Webs
A Food Web in the Arctic Tundra Identify the producers, 1 2 3 & 4 consumers in this food web
Energy Loss Some energy: Ø lost as waste Ø lost as uneaten material Ø passes to decomposer level Ø passes to next trophic level Only 10% of available energy passes to next level
Energy and the Food Chain • If 10% of the energy can be transferred from one trophic level to the one above it, each trophic level must have 10 x the energy as the one above it. • But this is limited by the rate that energy is being fed into the system
Energy and the Food Chain • The number of trophic levels depends upon the number of primary producers in the first trophic level • Biomes with small numbers of primary producers have short food chains
Limiting Factors In Energy Flow • Low conversion efficiency because: • not all material at any trophic level is consumed • not all material ingested is digested – roughage • most material digested used for catabolic processes • to provide organism with its energy requirements
The 10% Rule • 10% rule is important because: • it places limits on potential number of trophic levels in a system
A Simple Energy Flow Calculation 1000 tonnes of primary producer 0. 1 tonnes of level 5 consumer Energy available is rarely sufficient to support large numbers of consumers in higher trophic levels Most food chains only have 5 trophic levels
Could we feed a larger population of humans if we ate only plants?
Trophic: Trophic Level Related to feeding Functional classification of organisms according to feeding relationships Autotrophic Able to produce organic material from inorganic chemicals and some source of energy (photosynthesis) 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 Heterotrophic Food Chain Food Web Require a supply of organic matter or food from the environment. Movement of energy and nutrients from one feeding group of organisms to another in a series that begins with plants and stops with carnivores and decomposers Interlocking pattern formed by a series of interconnecting food chains
Summary Primary Producer plant/ algae Primary consumer herbivores Secondary consumer primary carnivore Tertiary consumer top carnivore autotrophs heterotrophs Quaternary consumer Usually no more than 5 links in a food chain. Why?
- Slides: 30