Biology Unit 3 Flashcards
State 3 ways energy can be lost along a food chain
Undigested materials
Movement
Heat
What is happening to the human population and food demands
It is increasing
Why are nitrates needed by plants
Nitrates produce amino acids which are used to make plant proteins
Name 2 ways that food yields can be increased
Use fertilisers
Gm crops
How do fertilisers help plants grow (4 steps)
- Fertilisers are added to soil to increase the nitrate content of the soil
- Nitrates dissolved in water are absorbed into plants
- The nitrates are used to make amino acids. These are combined to make plant proteins
- Animals eat plants to obtain amino acids for protein synthesis
What happens if fertilisers get into fresh water (5 steps)
- Fertilisers can leach into water
- There is an increase in algal populations, this is known as algal bloom
- Algal blooms reduce light levels, killing aquatic plants
- The dead plants become food for bacteria. The bacteria increases greatly in number
- The bacteria use up large quantities of oxygen, reducing the oxygen availability for other organisms such as fish
What are pesticides
Alternatives to fertilisers which kill pests that harm crops and prevent damage to crops
What is bioaccumulation
Pesticides sprayed onto crops can accumulate in the bodies of organisms over time. As they are passed along food chains, toxicity increases and can reach lethal levels.
How can GM crops be used as an alternative to fertilisers
GM crops have had new genes introduced into their DNA to give them improved characteristics. This may be larger yields or better resistance to pests
What is biological pest control
This is using animals to control the pests in an area. Farmers having cats to catch mice is a common example.
What is algal bloom
When algal populations in waterways increase due to extra unwanted nitrates entering the system
Describe the three steps of speciation
1:Isolation: Part of a population becomes isolated by an isolation barrier
2: Mutation: Over a long period of time different mutations will occur in each sub population
3: Natural Selection: There will be different selection pressures acting in two groups. Each sub-population evolves until they become so genetically different that they are 2 different species
Define speciation
Speciation is the process of a new species evolving
Describe the 4 steps of natural selection
- Species produce more offspring than the environment can sustain
- The best adapted individuals in a population survive
- The survivors reproduce and pass on favourable alleles with the selective advantage
- The favourable allele increase in frequency within the population
State the 3 possible effects of mutation on an organism
Neutral
Positive
Negative
