Chapter 13 Energy and Ecosystems Flashcards
What is an ecosystem?
An ecosystem is a particular area and all the living and nonliving components found there. This includes all the biotic and non-biotic factors that affect populations.
What is a primary producer?
Primary producers are organisms that are capable of making their own glucose. This includes plants and algae that make glucose by photosynthesis and bacteria that can make glucose through chemosynthesis..
What is a consumer?
Consumers are organisms that feed on other organisms for food.
What are trophic levels?
Trophic levels are categories in a food chain based on their position in the chain.
What is biomass?
The total mass of living material in a specific area at a given time. It is often measured in kg m-2 yr-1
How is biomass measured?
The sample is dried (in an oven at a low temperature), then weighed at regular intervals until the mass is constant (so you know all the water has been removed). The sample is then placed in a calorimeter.
Draw a diagram of a simple calorimeter.
Draw a diagram of a bomb calorimeter.
How is dry mass used?
Once the dry mass for a small area is determined it can be used to estimate the biomass for a larger area.
How do you use a calorimeter?
- Burn a sample of dry biomass in the colorimeter.
- The energy from burning is used to heat a known volume of water.
- The change in the temperature of the water is used to estimate the chemical energy in the sample.
Give 3 limitations of a simple calorimeter.
- It can take a long time to fully dehydrate samples. This is because it must take place at low temperatures to avoid burning.
- Precise measuring equipment (scales and thermometer) is needed for results to be accurate.
- Not all heat energy gets transferred to the water. This reduced accuracy.
What is Gross Primary Production (GPP)?
The total amount of chemical energy converted by plants, in a given area.
What units are used for Gross primary Production on land?
What units are used for Gross primary Production in aquatic environments?
In aquatic environments GPP is measured per unit volume: kg m-3 or kJ m-3.
How is Gross Primary Production different from Gross Primary Productivity?
Gross Primary Productivity refers to the rate of production so must be expressed per unit time.
Example:
MJ m–2 y-1 (megajoules per square metre per year)
kg km-2y-1 (kilograms per square kilometre per year)
How much of the energy that falls on plants is absorbed by chloroplasts and used for photosynthesis?
Only about 1% of the light that hits a leaf is used for photosynthesis.
What happens to the light that hits a leaf but is not used for photosynthesis?
- It is reflected off the leaf.
- It is transmitted through the leaf without hitting a chloroplast.
- It is transferred to heat energy.
- It is not absorbed by the chloroplast because it is not a wavelength the plant can use. Most plants do not use green light (495-570nm).
What is Net Primary Production?
This is the energy that is available to the herbivores that eat the plant after the respiration of the plant has been taken into account. It is expressed as energy per unit area (or volume).
It can be easily calculated as:
NPP = Gross primary production - respiration
What is net primary productivity?
This is the NPP per unit time as productivity is a rate.. Like Gross primary productivity it is expressed as:
Mj m–2 y-1 (megajoules per square metre per year)
kg km-2y-1 (kilograms per square kilometre per year)
What are decomposers?
Decomposers are organisms that consume dead plant and animals and release organic nutrients back into the environment. They are an essential part of nutrient cycles.
Give examples of decomposers.
Bacteria and fungi.
How do decomposers digest their food?
Decomposers secrete digestive enzymes onto the surface of dead organisms digesting them into soluble molecules that can be absorbed by the decomposers.
How are fungi adapted to have symbiotic relationships with plants?
Fungi have thin filaments called hyphae that can interact with plant roots and increase the surface area for water and mineral absorption.
What are the benefits to the plant and to the fungi of this relationship?
The plant increases nutrient and water uptake and in turn the fungi receive glucose from the plant.
What are these relationships between plants and fungi called?
Mycorrhizae
What is secondary productivity?
Secondary productivity is the production of organic matter by a consumer.
Eg: the growth of a caterpillar
Why is secondary productivity important?
Farmers need to know what the productivity of an animal is over time. This will aid in decisions about temperatures, food supplies and slaughter time.
Roughly how much energy is lost between trophic levels?
It varies but is usually around 90%.
Give 3 ways that energy is lost between trophic levels.
- Respiratory loss to the environment (mostly heat)
- Undigested food (lost in faeces and urine).
- Inedible parts of the organism consumed.
How is the net production of consumers calculated?
N = I - (F + R)
Net production of consumers = ingested food - (energy lost in faeces and urine + respiratory losses)
What is the theoretical yield of a crop?
This is the biomass that is possible under ideal conditions.
What is actual yield?
This is the biomass actually produced.
What is % yield?
% yield = (actual yield ÷theoretical yield x 100
How can farmers increase % yield in plants?
By reducing the energy lost by crops to pests.
By reducing weed species.
Use fertilisers.
Why do agricultural systems require fertilisers?
When crops are harvested nutrients are removed from the system and adding fertilisers replaces these lost nutrients.
What mineral ions are usually found in fertilisers?
Fertilisers contain nitrogen, phosphorus and potassium.
What are the benefits of using natural fertilisers?
- They improve soil structure.
- Nutrients are slow release.
- It is better for the environment.
What are 3 drawbacks of natural fertilisers?
- The nutrients are not very concentrated so large quantities are needed.
- The release may be too slow.
- Can be messy as they are made of manure, compost and other decomposing materials.
What are 3 benefits of artificial fertilisers?
- Easy to apply evenly and cleanly as they are powders or pellets.
- Concentrations of nutrients added are easy to determine.
- Smaller amounts are needed as they are concentrated
What is the main drawback of artificial fertilisers?
Excess artificial fertilisers dissolve in rainwater and leech into rivers and ponds leading to eutrophication.
Give 3 ways that farmers can reduce the loss of crops to pests.
- Use of insecticides to kill insect pests.
- Use of herbicides to kill weeds.
- Use of biological control agents.
What is biological control?
The use of natural predators to control pest species.
Examples: Ladybirds will eat greenfly
Parasitic wasps lay eggs in caterpillars, killing them.
How can farmers increase % yield in livestock?
Reducing the energy lost through respiration.
Give ways 2 a farmer can reduce energy lost through respiration in livestock.
- Keep animals from moving to reduce energy expenditure.
- Keep animals warm to reduce respiration to maintain body temperature.
What do plants and animals need nitrogen for?
All living things require nitrogen for the production of proteins and nucleic acids (DNA and RNA).
Why can organisms not use the nitrogen in the air?
The air is 78% nitrogen but the strong double bond in nitrogen gas makes it unavailable to most organisms.
How can nitrogen gas be converted into other nitrogen containing compounds?
Nitrogen fixation by bacteria results in nitrogen gas getting converted into ammonia. Rhizobium is a species of bacteria capable of doing this.
Where are nitrogen-fixing bacteria found?
These bacteria are found in the soil or in the root nodules of legumes like peas and clover.
What is ammonification?
Ammonification is the conversion of nitrogen in waste products (urine and faces) into ammonia.
What type of organism is capable of ammonification?
Saprobionts. These are a type of decomposer - bacteria and some fungi.
What happens to the ammonia and ammonium ions on the soil?
Ammonium ions get converted into nitrites and then nitrates by nitrifying bacteria.
Give an example of a species of nitrifying bacteria that convert ammonium ions into nitrites.
Nitrosomonas
Give an example of a species of nitrifying bacteria that can convert nitrites to nitrates.
Nitrobacter
Why are nitrates useful to plants?
Nitrates are soluble in water so can be easily absorbed by plants.
Why is denitrification important?
Denitrification returns nitrogen gas to the atmosphere and maintains the cycle.
What do denitrifying bacteria do?
Denitrifying bacteria use nitrates in the soil during respiration and release nitrogen gas. This happens in anaerobic conditions.
How does nitrogen get from plants into animals?
The animals eat the plants.
Draw a simple flow chart to represent the nitrogen cycle.
What do plants and animals need phosphorus for?
Phosphorus is used by all living things to make phospholipids, nucleic acids and ATP.
How does phosphorus in rocks end up in bodies of water?
Rocks weather to release phosphorus in the form of soluble phosphate ions (PO43-)
How do plants access phosphate?
Phosphates are soluble so plants are able to absorb the ions through their roots. ALgae can absorb phosphates directly from the water.
How do phosphates get from plants to animals?
Feeding.
What type of organisms can release phosphate ions from dead plants and animals and waste products?
Saprobionts.
How do phosphates end up back in rocks?
The phosphates get trapped in sediments which will become rock over very long geological time periods.
Draw a simple flow chart to represent the phosphorus cycle.
Why do plants require magnesium?
To make chlorophyll.
Why do plants require calcium?
Calcium is used to make the middle lamella. This is the part of the cell wall that helps plant cells to stick together.
Briefly describe how you could investigate the effect of a mineral deficiency on plant growth.
- Produce a solution containing all nutrients and a series of solutions that only lacking one nutrient.
- Place genetically identical plantlets in test tubes containing the different solutions and grow them in identical conditions (appropriate light intensity and temperature).
- After 2 weeks make qualitative observations and quantitative measurements of growth.
What observations would indicate nitrate deficiency in a plant?
Reduced growth (compared to control)
Yellowing of leaves (chlorosis)
What observations would indicate phosphate deficiency in a plant?
Reduced growth (compared to control)
Necrotic spots on leaves
What observations would indicate magnesium deficiency in a plant?
Reduced growth (compared to control)
Interveinal chlorosis (no Mg for chlorophyll)
What observations would indicate calcium deficiency in a plant?
Reduced growth (compared to control)
Weakened stem resulting in wilting (no middle lamella)
