Section 5 - Chapter 13: Energy and Ecosystems - old Flashcards
What do plants convert light energy into and what is it used for?
- Plants convert light energy into chemical energy
- In order to make organic compounds like glucose
- Make other groups of biological molecules forming biomass
What are the 3 groups of organisms according to how they obtain energy?
- Producers - photosynthetic organisms that produce their own energy
- Consumers: Eat other organisms
- Saprobionts: (decomposers) break down dead organisms. Contribute to recycling of nutrients as they release minerals to plants.
What is a food chain
- Describes a feeding relationship in which producers are eaten by primary consumers then secondary consumers.
- Each stage is referred to a trophic level.
- Arrows show energy flow
What is a Food Web
- Many food chains linked together.
What is Biomass and what is its units
- Is the total mass of living material in a specific area at a given time.
- Biomass is measured using dry mass as fresh mass has varying water
- Units are gm-2 on land and gm-3 on water
How to prepare fresh mass into dry mass
- Heating a sample up to 100 degrees to evaporate water
- Weighing until no further change in mass
Why is Calorimetry used
- Calorimetry can be used to estimate the chemical energy store in biomass (the amount)
How does Calorimetry work
- Weighing dry material and burning it in pure oxygen in a sealed chamber - bomb
- Bomb surrounded by water bath and measuring the temp rise of surrounding water
- We know the specific heat capacity, know volume and temp rise. Can calculate energy released by the mass of burnt biomass (KJkg-1)
Exam Questions:
a) Suggest how you could determine the dry mass of a sample of plant material (2)
b) What is the advantage of using dry mass and not fresh mass to compare the yield of a plant?
- a) 1. Heat at 100 degrees to evaporate water. 2. Weigh and heat until no further change in mass
- b) 1. Amount of water will vary. 2. Will affect fresh mass/ not dry mass
How much solar energy is used to make new plant biomass
- Only a tiny percent of solar energy available is incorporated into new plant molecules
Why is the % of solar energy available used in plants so low?
- Over 90% of the sun’s energy is reflected back into space by clouds and dust.
- Not all wavelengths of light can be absorbed for photosynthesis
- Light may not fall on a chlorophyll molecule
- Limiting factors may limit rate of photosynthesis and energy storage (CO2)
What is GPP
- Gross Primary Production
- The total quantity of the chemical energy stored in plant’s biomass, in a given area and time is GPP
How much of the GPP is used in respiration and in the plant’s biomass
- Plants use 20-50% of the GPP in respiration
- The remaining energy is stored as biomass
What is the calculation to calculate NPP
- NPP = GPP - Respiratory losses
What is NPP
- Net primary production
- Amount of energy left after respiration which is available for plant growth and reproduction
- Available to primary consumers in the next trophic level.
What is the % of npp used by primary consumers, secondary/tertiary
- Less than 10% of npp is used for primary consumers
- Secondary and tertiary are slightly more efficient 20%
Why is a low percentage of energy transferred at each stage
- The whole organism is not consumed
- Some of the energy is lost through urine and faeces
- Some energy is lost to the environment as heat from respiration
- Some parts of organism are not digested
It is the relative inefficiency of energy transfer between trophic levels that explains why:
- Most food chains have only 4-5 trophic levels
- Total mass of organisms (biomass) is less at higher trophic levels
- Total amount of energy available is less at each level
What is calculating the NPP good to scientists. Which has a higher NPP: Desert or Tropical Rainforest
- Can compare different ecosystems.
- The availability of light, water, nutrients are different in areas,
- Tropical Rainforest has higher NPP than Desert
How can farmers increase Primary Productivity
- Removing factors that inhibit plant growth such as predators and disease
- Improving conditions for photosynthesis
- Increasing ground coverage - allows maximum solar energy to be used
Exam Question: Explain how farming practices increase the productivity of agricultural crops
- Fertilisers/ named nutrient e.g. nitrate - proteins, phosphate - ATP
- Pesticides/herbicides (removing competition)
- Selective Breeding/ genetic modification
- Greenhouses enhance conditions for photosynthesis
- Ploughing - aerates soil
- Crop rotation
- Watering
- Protection of crops
What happens when fertilisers are used - advantages
- Nitrogen used to make ATP and DNA
- Causes plants to grow and have big Surface Area
- Increases rate of photosynthesis
- Increased Productivity
What are the problems with fertilisers and what can they do to harm the environment
- Eutrophication - leaching causes over-enrichment of water with nutrients leading to excessive algal growth and reduced oxygen levels
- Reduced Species Diversity - Nitrogen rich soils can favour species which can out compete others
What is leaching
- Soluble chemical/ mineral drain away from soil by the action of percolating liquid (rainwater)
- Eutrophication :Ends up in freshwater/ drinking lakes - stomach cancers, oxygen transport
What is algae
- Large group of eukaryotic, simple non-flowering plants containing chlorophyll but lacking true stems, roots and leaves
What is Phytoplankton
- Photosynthesising microscopic organisms that inhabit the upper sunlit layer of almost all oceans and lakes
What is Cyanobacteria
- Blue/green bacteria/ algae that obtain their energy through photosynthesis
Exam Question: Nitrate from fertiliser is applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water
- Growth of algae blocks light
- Reduced photosynthesis so submerged plants die
- Saprobiotic bacteria
- Aerobically respire
- Less oxygen for fish to respire so aerobic organisms die
How can humans increase secondary productivity energy transfer between producer and consumer
- Animals are culled when they are young, as they have a higher secondary productivity
- Antibiotics used to avoid any energy loss to pathogens
- Selective breeding produce livestock with faster growing rates and increased production
- Some animals are kept in confined spaces
What is factory farming and what happens to the animals
- Keeping animals in small enclosures can help reduce energy loss
- This restricts movement, decreasing energy lost in muscle contraction
- Feeding is controlled to prevent wastage and provide optimum amount of food
- This enclosure excludes predators
What are the advantages of factory farming
- Efficient energy conversion
- Produces low cost food
- Easier to prevent disease from being introduced
- Easier to isolate ill animals
What are the disadvantages of factory farming
- Animals vulnerable to spread of disease
- Use of drugs - leads to antibiotic resistance
- Unnatural conditions may cause stress to the animal
- Restricted movement may cause osteoporosis and join pain
Exam Question: Give a biological molecule that contains: Nitrogen and Phosphorous
- Nitrogen - Amino acid/ protein/ enzyme/ DNA/ RNA
- Phosphorous - DNA/RNA/ ATP/ ADP/ NADP
What form can plants take nitrogen by which can they not?
- Can’t use nitrogen in the gaseous form
- Most of the plant’s N is taken up at the root hairs in NO3 by active transport
What is the sequence of all nutrient cycles
- The nutrient is taken up by producers as simple, inorganic molecules
- The producer incorporates the nutrient into complex organic molecules
- When the producer is eaten, nutrients pass into consumers
- It then passes along food chains
- When the producers and consumers die, their complex molecules are broken down by saprobiontic microorganism
What are the key stages of the nitrogen cycle
- Nitrogen Fixation
- Ammonification
- Nitrification
- Denitrification
What happens in Nitrogen Fixation
- The fixing of gaseous Nitrogen into N containing compounds to ammonium ions then to ammonia
Briefly explain what happens to nitrogen in nitrogen fixation
- Done by 2 ways:
- Mainly done by free living nitrogen fixing bacteria - these bacterias reduce gaseous nitrogen into ammonia
- Mutualistic nitrogen-fixing bacteria - these bacteria live in nodules of leguminous plants like peas and beans. Provides plant with nitrogen compounds and the plant provides the bacteria with carbohydrates
What happens in Ammonification
- Following death - breakdown of N compounds into ammonia
- Faecal waste brwakdown : releases ammonia by saprobionts which release ammonium ions into the soil
- Dead organisms: during breakdown get removal of NH2 to form ammonium ions.
What do saprotrophic micro-organisms do in the final stages of decomposition
- They release hydrolytic enzymes from their hyphae, breaks down complex organic molecules.
- The digested products can then be absorbed and used for respiration
What happens in Nitrification
- Carried out by free-living soil microorganisms called nitrifying bacteria called nitrifying bacteria
- Occurs in 2 stages:
- Oxidation of ammonium ions into nitrite ions
- Oxidation of nitrite ions into nitrate ions
What do nitrifying bacteria require
- Requires oxygen to carry out these conversions.
Exam Question: Describe the role of microorganisms in producing nitrates from the remains of dead organisms
- Saprobiotic break down remains into ammonium
- Ammonium ions into nitrite ions then nitrate by nitrifying bacteria
Exam Question: Denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil
- Fertility increased as more nitrate formed
- Less/ no denitrification
What happens in denitrification
- Anaerobic denitrifying bacteria using nitrate in respiration
- Converts nitrates back into gaseous nitrogen
Why do plants and animals need phosphorous
- Need phosphorous to make biological molecules such as phospholipids, DNA and ATP
Where is phosphorous found and form is is when it is dissolved
- Phosphorous is found in rocks and exists mostly as phosphate ions when it is dissolved
Describe the Phosphorous Cycle
- Phosphate ions in rocks are released into the soil by weathering
- Phosphate ions are taken up by plants through the roots
- Ions transferred through food chains (animal eats plants)
- Ions lost from animals in waste
- When plants and animals die, saprobionts are involved in breaking down organic compounds, urine and faeces, releasing phosphate ions back into soil
- Weathering of rocks also releases phosphate ions to rivers which is taken up by aquatic producers (algae)
- Geological uplift pushes new rock to the surface
8.
Exam Question: Other than spreading fertilisers, describe and explain how 1 farming practice results in addition of nitrogen-containing compounds
- Growing Legumes, Allow cattle to graze, add dung, spread/add manure
What is a mycorrhiza composed of
- It is a symbiotic association composed of a fungus and roots of a vascular
What do mycorrhiza do
- Acts like a sponge
- The fungi colonize the root system of a host plant acting like extensions of the root system increasing the surface area for water and nutrient absorbance
- They have mutualistic relationship with the plant as the plant provides the fungi with carbohydrates
Exam Question: Suggest 1 source of the phosphate in the lake
- Fertilisers, detergents, manure, slurry
Exam Question: Suggest and explain why a poor supply of phosphate ions results in poor growth of plants
- Required to make ATP/ GP so less respiration
- Required to make nucleotides so less DNA, mRNA, tRNA for cell division or production of proteins
- Required to make RuBP/NADP so less CO2 reduced into sugar
- Required to make phospholipids for membranes
What are the 2 types of fertilisers
- Natural
- Artificial
What do natural fertilisers consist of
- Dead/decaying remains of plants and animals and their waste
What do artificial fertilisers consist of
- Mined from rocks and deposits are converted into a form that has an appropriate balance of minerals
- Nitrogen, phosphorous and potassium are always present
