Unit 18: Energy and Nutrient Transfer

1. Section 18.1 Food chains and food webs? Section 18.2 Pyramids of numbers and biomass Section 18.3 Energy Flow in Ecosystems Section 18.4/18.5 Cycles of Matter Unit 18:Energy and Nutrient Transfer

2. Numbers in a Food Web • Number Pyramid: • Shows the numbers of organisms in a trophic level for a specific food chain • Example: • 1 fox eats 25 birds • 25 birds eat 250 grasshoppers • 250 grasshoppers eat 3000 grass plants • Does not show the size of the individuals • 2) Size Pyramid: • Shows the relative size of each organism in the food chain • Example: • 1 tree supports 1500 caterpillars • 1500 caterpillars feed 100 birds • 100 birds feed 1 sparrowhawk 1 100 1500 1

3. Biomass in a Food Web • 3) Biomass Pyramid • All living material in a trophic level is its biomass • Average dried of weight of all organisms in an area • 35% of animals weight • 20% of plant weight • Remove H2O to see real weight of organic molecules • biomass of the levels decreases • Why does the Energy Pyramid explain this? • There is less energy to keep more complex organisms alive • The since every trophic level depends on the one under it, they are also limited by them • Land ecosystems rarely have more than 4 trophic levels

4. Energy and the Future • Based on what we have talked about, what is the based diet for a growing poor nation? • Vegetarian • Why? • It is more efficient. Eating producers cuts out 90% of wasted energy in the ecosystem • If eating plants is more efficient, why do we need to eat so much? • Most of the energy is in cellulose, which we can’t digest, so it is waste • Meat gives us more energy but costs more: • 0.5 kg or beef needs 2.5kg of plant material • What would be a better alternative to meat? • Insects 80kgs for every person

5. State which type of pyramid each is Energy Pyramid Number Pyramid Biomass Pyramid

6. Recycling Matter • Energy must be transferred through trophic levels to power an ecosystem • Stability comes from constant supply of new building materials • Members in the food chain need to reproduce • Need elements (C, N, H, P, S) to build organic molecules • 4 Biogeochemical Cycles • Biological processes living things breaking down material • Geological processes geologic activity breaking down rocks and minerals • Chemical/Physical processes clouds, lighting, rain, snow and other weather • Human Activity Human development; building and farming

7. Natural Cycles on Earth • Water Cycle: • Evaporation • Water absorbs energy from the Sun and evaporates to water vapor; also transpiration • Condensation • Water vapor slowly collects over time to form clouds • Precipitation • Clouds grow heavy and rain, snow, hail, etc… falls to the Earth • Accumulation • Water runs together on the ground to form lakes, rivers, stream, and underground reservoirs • Repeat • Water eventually moves back to the oceans or evaporates and the cycle starts again

8. Natural Cycles on Earth • 2)Carbon Cycle: • Animals, fire, and geothermic activity send CO2into the atmosphere • Living things die and return carbon to the environment • CO2dissolves into rain clouds and oceans • CO2 is pulled into plants/algae and used in photosynthesis • Other living things feed on carbon compounds like carbohydrates • Carbon returns to the cycle

9. Natural Cycles on Earth • 3) Nitrogen Cycle: • All living things need Nitrogen but most is in N2gas which cant be used; need nitrates (nitrogen containing molecules) • Nitrogen fixation changing N2 to NH3, NO2-, and NO3- • Sources • Decomposers:release ammonia (NH4+) as they break down material • Nitrifying bacteria: change ammonia (NH4+) to nitrates • Nitrogen-fixing bacteria: live in the soil or root nodules of plants; change N2 into NH4+ • Lightning: energy reacts N2 with O2 to form Nitrates; leach into soil through rainwater • Denitrifying bacteria balance N2 in air by changing excess nitrates back into N2

10. Natural Cycles on Earth • 4) Phosphate Cycle: • All living things need phosphates to build DNA and RNA • Most phosphate is trapped in rocks and sediment layers in the Earth (Geological uplifting) • Rivers and water sources breakdown rocks over time and leach phosphates into water sources • Decaying organisms recycle phosphates into the ecosystem

11. Limits to Growth • Why don’t we see a much larger biomass on Earth? • Every environment has a limit keeping it in check • Energy and nutrients can limit growth, however more often limited amounts of nitrogen or phosphorous stop excessive growth • Nitrogen is less common in saltwater environments • Phosphorous is the less common in freshwater environments