Bio P2

How do new pathogens affect a community?

Populations may not have immunity to the pathogen and are consequently wiped out

How does competition affect a community?

1. If two species compete for the same resources and one is better adapted, that species will outcompete the other. 2. This may continue until there are too few members of the lesser adapted species to breed successfully

What is trophic level?

The position of an organism within a particular food chain

What is the link between trophic level and organisms?

Trophic level 1 = Producer Trophic level 2 = Primary consumer Trophic level 3 = Secondary consumer Trophic level 4 = Tertiary consumer

What do producers do?

Make their own food

What do primary consumers do?

Eat producers and transfer chemical energy from plant tissues into their own

What do secondary consumers do?

Eat primary consumers and gain energy from their tissues

In the food chain, what happens to energy in waste or dead matter?

Transferred to decomposers (bacteria and fungi) who break down dead organisms and waste, recycling nutrients back into the ecosystem

What is biomass?

Mass of living matter

Why are pyramids of biomass always pyramid shaped?

Available biomass always decreases at higher trophic levels

Why are pyramids of energy always pyramid shaped?

Energy is lost from food chains at each trophic level

Why is energy lost between trophic levels?

-Consumers are unable to digest and absorb all the chemical energy stored in food organisms -Not all of the consumed organism is eaten (claws, fur, bones) so not all energy is transferred -Not all ingested material is digested and absorbed as some is egested as faeces -Not all energy is converted to biomass (heat loss, excretion)

How is carbon taken up by living organisms?

It is taken out of the atmosphere in the form of CO2 by plants during photosynthesis

How is carbon transferred between living organisms?

-When herbivores eat plants -When carnivores eat herbivores

How is carbon released into the atmosphere?

-Respiration in plants and animals releases CO2 -Bacteria and fungi release CO2 during decomposition -Combustion (burning of fossil fuels) releases CO2

What does nitrogen fixation do?

Makes nitrogen available to living organisms

What do nitrogen fixing bacteria do?

Convert N2 gas into ammonium compounds, which are then converted to nitrates in the soil

How can nitrogen fixation occur?

-Free-living bacteria in the soil -Bacteria in the root nodules of leguminous plants -Lightning -Production of chemical fertilisers

How is nitrogen transferred between living organisms?

1. Animals feed on plants and digest the proteins in the plant tissues, providing nitrogen to build animal proteins 2. Nitrogen is then passed up the food chain

How is nitrogen released?

1. Decomposers return nitrogen from dead organisms and metabolic waste to the soil as ammonia 2. Ammonia reacts with water in the soil to form ammonium ions 3. Nitrifying bacteria convert ammonia into nitrites, then into nitrates, which can be taken up by plants

What is nitrification?

A process that breaks down ammonia into nitrites or nitrates

What do denitrifying bacteria do?

Convert nitrates back into N2 gas, returning it to the atmosphere

What is denitrification?

The conversion of nitrates into nitrogen

How do farmers reduce denitrification?

Plough soil to increase aeriation as denitrifying bacteria are only present in anaerobic conditions

What is the consequence of carbon monoxide pollution?

Suffocation and death in high concentrations

What is the consequence of sulfur dioxide pollution?

Causes acid rains which causes respiratory problems in humans

What is a greenhouse gas?

A gas that absorbs infrared radiation from the Sun so it remains trapped in the Earth's atmosphere

What is the greenhouse effect?

A natural process by which heat is trapped in the Earth's atmosphere

What is the purpose of the greenhouse effect?

Keeps Earth warm enough to support life

What are examples of greenhouse gases?

-Water vapour -CO2 -Methane -Nitrous oxides CFCs

Which greenhouse gases have increased due to human activities? Why?

-CO2 due to the combustion of fossil fuel -Methane due to cattle digesting grass

What happens in the greenhouse effect?

1. Sun emits radiation to Earth's atmosphere 2. Earth's surface absorbs some heat and reflects the rest back to space 3. Some is absorbed by greenhouse gases and trapped within the atmosphere

What is the enhanced greenhouse effect?

When increasing levels of greenhouse gases from human activities trap more heat in the atmosphere

What is the result of the enhanced greenhouse effect?

Earth's average temperature rises above normal, leading to global warming and climate change

What are the consequences of global warming?

-Increased ocean temperatures (polar ice caps melt, sea levels rise, flooding) -Increased temperatures causing extreme weather (super storms, flooding, droughts) -Loss of habitat due to extreme weather -Decreased biodiversity, increased extinction rate -Increased migration of species, including pests and disease

What conditions can farmers control in glasshouses to increase rate of photosynthesis? How do they control this?

-Temperature (artificial heating) -Light intensity (artificial lighting) -Water (regular watering) -CO2 concentration (increased CO2 in the air)

What is a polythene tunnel?

Large plastic tunnels that cover crops

What is the purpose of a polythene tunnel?

Protect outdoor crops from: -Weather (high winds, rain, extreme temperatures) -Increase temperature inside the tunnel -Prevent pests from entering

What do fertilisers do?

Increase amount of key nutrients in the soil, leading to crops growing and being more healthy (increased yield)

What are the two types of fertilisers?

Chemical, organic

What is an example of an organic fertiliser?

Manure

What are pesticides?

Chemicals that kill unwanted species

What is the purpose of pesticides?

They reduce damage to crops and increase yield

What are some examples of pesticides?

Insecticides, herbicides, fungicides

What are advantages of using pesticides?

-Easily accessible and relatively cheap -Have an immediate effect -Kills the entire population of pests

What are disadvantages of using pesticides?

-Pests may develop resistance -May kill other beneficial organisms (bees) -May cause bioaccumulation -Need to be repeatedly applied

What is biological control?

The use of a natural predator to eat the pest species

What are the advantages of using biological control?

-No pollution -No resistance -Can target specific species -Long lasting -Does not need to be repeatedly applied

What are the disadvantages of using biological control?

-May eat other organisms instead of the pest -Takes longer to become effective -Cannot kill an entire population -May not adapt to new environment and may move out -May become a pest itself

What is yeast?

A single-celled fungus that can respire aerobically and anaerobically

What microorganism is used in bread making?

Yeast

How does yeast cause bread to rise?

The yeast breaks down the sugars in the bread in anaerobic respiration and produces carbon dioxide which causes the bread to rise

What is the word equation for the anaerobic respiration in yeast?

Glucose -> Ethanol + Carbon dioxide

Which bacteria is used to make yogurt?

Lactobacillus

How is yogurt produced?

1. Equipment is sterilised 2. Milk is pasteurised at 90C to kill unwanted bacteria 3. Milk is cooled to 40C and lactobacillus is added 4. Mixture is incubated at 40C for several hours, while the lactobacillus digests milk proteins and ferments the sugar in the milk 5. Lactobacillus converts lactose into lactic acid (increased acidity sours and thickens the milk to form yogurt) 6. Yogurt is stirred and cooled to 5C to stop lactobacillus

In the production of yogurt, why is equipment sterilised and why is milk pasteurised?

-Kill unwanted bacteria (as it could slow down the production of yogurt as the bacteria would compete with lactobacillus for lactose) -Prevent chemical contamination (would spoil the yogurt taste)

How does lactobacillus lowering the pH of milk help the yogurt?

-Prevents growth of other microorganisms -Yogurt can be kept for a longer time

What are fermenters?

Containers used to grow 'culture' microorganisms like bacteria and fungi in large amounts

What is the main advantage of a fermenter?

Conditions can be carefully controlled to produce large quantities of the right microorganism

What conditions are controlled inside a fermenter?

-Oxygenation -pH -Temperature -Nutrients -Agitation

What is selective breeding?

The selection of individuals with desirable characteristics and then breeding them together

What are the stages of selective breeding?

1. Individuals with desirable characteristics are bred together 2. Offspring with desired characteristics are bred together 3. Process is repeated over many generations until desired characteristics are in all offspring

What are examples of desirable characteristics in plants?

-Disease resistance -Increased crop yield -Harsh weather resistance -Better tasting fruits -Large or unusual flowers

What is the main problem of selective breeding? What are the risks?

Inbreeding results in: 1. A reduction of the gene pool which reduces number of alleles in a population 2. Limited gene pool leads to increased chances of organisms inheriting harmful genetic defects and organisms being vulnerable to disease

What are the differences between natural selection and selective breeding?

Natural selection: -Occurs naturally -Resultant populations have features that are more adapted to their environment and survival -Takes a long time to occur Selective breeding: -Occurs due to human intervention -Resultant populations have features that are useful to humans -Takes less time

What is genetic modification?

The transfer of a gene or a section of DNA from one organism to another

What are the stages of genetic modification?

1. Locate desired gene 2. Restriction enzyme cuts the required gene out of the DNA, resulting in pieces of DNA with 'sticky ends' 3. Same restriction enzyme cuts a bacterial plasmid 4. Plasmid and isolated gene are joined together by DNA ligase enzyme 5. Genetically engineered plasmid cell is inserted into a bacterial cell 6. Bacteria reproduces, plasmid is copied forming a recombinant plasmid 7. Recombinant plasmid spreads and gene is expressed, human protein is produced 8. Bacteria can be placed in a fermenter to produce a greater quantity of human protein faster

How are plasmids and viruses useful in genetic engineering?

They take up pieces of DNA and insert this recombinant DNA into other cells

In genetic engineering, where do viruses transfer DNA? Where do plasmids transfer DNA?

Viruses: Human cells/bacteria Plasmids: Bacteria/Yeast

What traits can genetically modified crops have?

-Resistance to insect pests -Resistance to herbicides -Produce additional vitamins and improved nutritional value -Resistance to droughts

What are the advantages and disadvantages of genetically modified crops?

Advantages: -Less chemicals used (better for environment) -Cheaper and less time-consuming for farmers -Increased crop yield Disadvantages: -Increased seed costs (harder for small farms to compete with large farms) -Increased dependence on certain chemicals (may become more expensive) -Inserted genes may be transferred by pollination to wild plants, reducing usefulness of GM crop -Reduced biodiversity due to increased herbicides use -GM crops don't grow as well as normal plants

What is transgenic?

The transfer of genes between different species

Which hormones regulate the menstrual cycle?

FSH, LH, Oestrogen, Progesterone

What is FSH released by?

Pituitary gland

What is the role of FSH?

Causes an egg to start maturing in the ovary

What are the effects of FSH?

• Stimulates the development of egg cells in the ovary - Stimulates the release of oestrogen

What is LH released by?

Pituitary gland

What is the role of LH?

Causes ovary to release a mature egg cell

What are the effects of LH?

• Stimulates release of an egg cell from the ovary (ovulation) - Stimulates the release of progesterone

When is LH released?

When oestrogen levels peak on day 14 (ovulation)

What hormones does progesterone limit the release of?

LH and Oestrogen

What are the two stages of protein synthesis?

Transcription and Translation

What happens in transcription?

DNA is transcribed and an mRNA molecule is produced

What happens in translation?

mRNA is translated and a protein is produced

What is mRNA?

messenger RNA

Where does transcription occur?

Nucleus

What is the sequence of events in transcription?

1. DNA molecule unzips due to hydrogen bonds between complementary bases breaking 2. mRNA nucleotides enter unzipped strand and bind to complementary nucleotides in the template (exposed) strand of DNA, forming a single mRNA strand 3. mRNA strand leaves through the nuclear pore

Where does translation occur?

Cytoplasm

What is tRNA?

Transfer RNA

What is the sequence of events in translation?

1. After leaving the nucleus, the mRNA strand attaches to a ribosome in the cytoplasm 2. Cytoplasm has free molecules of tRNA, which have a triplet of unpaired bases (anticodon) at one end and an amino acid at the other 3. Anticodon on each tRNA molecule pairs with a complementary codon on mRNA strand 4. When neighbouring anticodons pair, a peptide bond is formed between their amino acids 5. Bonding continues until a stop codon on mRNA is reached, signalling that amino chain is complete 6. Amino chain is folded and modified to form final protein molecule

What is codominance?

When both alleles within a genotype are expressed in the phenotype of an individual

What is deforestation?

The large scale clearing of trees

What are the negative effects of deforestation?

Leaching, Soil erosion, Water cycle disturbance, Carbon cycle disturbance

How does deforestation cause leaching?

Soil minerals are not taken up by trees and are instead washed away by rain into nearby bodies of water

How does deforestation cause soil erosion?

Soil is not held together by tree roots and organic matter, so is more likely to be washed or blown away

How does deforestation disturb the water cycle?

Less water is released into the atmosphere by transpiration, reducing cloud formation and rainfall

How does deforestation disturb the carbon cycle?

Less photosynthesis causes increased carbon levels in the atmosphere

What do fish farms do?

Raise large numbers of fish in a small space to provide food for humans

What advantages do fish farms have over fishing?

• High quality, fast-growing fish due to selective breeding - Protection against predators - Quality of water is controlled (no pollution) - Fish grow rapidly due to controlled feeding

In fish farms, what is yield?

The fast growth of healthy fish