Unit 3 Flashcards
Biotic factors
Living factors:
Disease
Predation
Grazing
Abiotic factors
Non-living:
Temperature
Rainfall
pH
Human influences
Air pollution
Habitat destruction
Overfishing
Desertification
Habitat
The place where an organism lives
Population
A group of organisms of the same species
Species
A group of organisms which can interbreed to produce fertile offspring
Biodiversity
The total variety of living things in an area
Community
All the populations living in the ecosystem
Ecosystem
The balance of community (living) plus habitat (non-living)
Producer
A green plant which makes its own food by photosynthesis
Consumer
An organism which needs to eat other organisms to gain energy
Herbivore
An animal which only eats plants
Carnivore
An animal which only eats other animals
Omnivore
An animal which wats both plants and animals
Predator
An animal which hunts other animals
Prey
An animal which is hunted by other animals
Niche
The role an organism plays in the community
When does competition occur?
Between organisms when resource are in short supply
Interspecific
Competition between members of different species for similar resources
Intraspecific
Competition between members of the same species for the exact same resources
Decomposer
Breaks down organic material (e.g. dead bodies and waste)
Food chain
The arrows show the direction of energy flow
What do animals compete with one another for if in short supply?
Food
Water
Shelter
Which type of competition is more intense?
Intraspecific as organisms are competing for the exact same resources
What do plants growing in the same habitat compete for if in short supply?
Light
Water
Soil nutrients
Interdependent
A delicate balance between predator and prey
Indicator species
Organisms that by their presence or absence give information about environmental quality and pollution levels
Water pollution
-Polluted by untreated sewage being allowed to enter rivers and streams
-Lots of organic waste
->lots of bacteria (decomposers)
->low oxygen levels (bacteria takes it in to respire)
Abundance
Number of that type of organism
Quadrats
Sample plants in fields
Count the number of squares containing your plant and then factor up for the total area of the field
-More than 1 quadrat thrown (reliable)
-Thrown randomly (valid) (unbiased)
-Spread across the field (representitive)
-Stick to rules (if a plant is half in and half out)
Pitfall trap
Sample small ground insects on the ground soil
-Multiple traps (reliable)
-Traps set up across the area (representative)
-Birds may eat trapped animals ->camouflage with leaves
-Some animals may eat other animals ->check traps regularly
Line transect
Measures the distribution of organisms from one point to another e.g. high shore to low shore
Quadrats placd at regular intervals along it and abiotic factors are measured
Relationships can be found between abiotic factors and distribution of organisms
Light intensity
Light meter
Shadows->stand without your shadow covering it
Light changes->carry out same time of day
Soil moisture
Moisture meter
Unclean probe->clean probe (cloth)
Different depths->same depth
Same position
What happens to energy at each level of a food chain
-90% of energy is ‘lost’ as heat, movement or indigestible materials
-10% of energy is used for growth and is passed on to the next level
Pyramid of energy
Always a pyramid
Shows the energy passed on from one stage in a food chain to the next
Pyramid of numbers
Shows the number of organisms at each stage of a food chain
Irregular pyramids of numbers
1-when a tree/bush is the producer
2-when parasites feed off of the top predator
What requires an increased food yield
Increasing human polulation
Fertilisers
-Provide plants with chemicals such as nitrates to increase crop yield
How do nitrates work in fertilisers?
-Nitrates dissolve in soil water and are dissolved into plants
-The plants use the nitrates to produce amino acids which are synthesised into plant protein
-Animals consume plants/animals to obtain amino acids for protein synthesis
Algal blooms
-Fertilisers leach into fresh water, adding extra, unwanted nutrients
—>increases algal populations
—>algal blooms
—>reduce light availability for aquatic plants->death
—>dead plants and dead algae become food for bacteria
—>bacteria grows in number
—>bacteria use up large quantities of oxygen
—>reduces oxygen availability for other organisms
—>reduced biodiversity in water
Alternatives to fertilisers
Genetically modified crops
Pesticides
Used to kill plants and animals that reduce crop growth
Biosccumulation
Pesticides sprayed on crops can accumulate in the bodies of organisms over time
As they are passed along food chain, toxicity increases and can reach lethal levels
Alternatives to pesticides
GM crops
Biological control
Biological control
The deliberate introduction of a predator to a parasite or pest
Advantages of biological control
-No chemicals added to food chains
-Introduced predator is specific to pest
-Much cheaper after initial set-up costs
Disadvantages of biological control
-Introduced species can sometimes become a pest
-Doesn’t guarantee that all pests will be killed
-Introduced predator can leave the environment
Mutation
A random change to the genetic material
Occur spontaneously
Only source of new alleles in a population
Environmental factors that can increase the rate of mutation?
Mutagenic agents
Chemicals e.g. mustard gas
Radiation e.g. x-rays, gamma radiation
Adaptation
An inherited characteristic that makes an organism well suited to survival in its niche in its environment
Desert plant adaptations
Surface area (leaves are spines to reduce water loss
Very deep roots (access deep underground water)
Thick waxy cuticle (reduce water loss and store water in flesh)
Speciation
The formation of different species from a common ancestor
Natural selection
-species produce more offspring than the environment can sustain
-Selection pressures e.g. lack of food, predation
-Those best adapted are more likely to survive and reproduce -> pass on favourable alleles to offspring
-Advantageous alleles will increase in frequency in a population
Steps of speciation
-Part of a population becomes isolated by an isolation barrier
-Different mutations occur at random in each sub-population
-Natural selection selects for different mutations in each group due to different selection pressures
-Each sub-population evolves separately until they become so genetically different that they are two distinct species
-If the two new populations are allowed to interbreed and cannot produce fertile offspring then they are now different species
Types of isolation barriers
Geographical- mountain, earthquake
Ecological- pH, salinity
Behavioural- becoming fertile at different times
Stages of speciation
-Isolation
-Mutation
-Natural selection
-Speciation
Types of pesticides
Fungicides - used to kill fungi
Insecticides - kill insects
Bactericides - bacteria
Herbicides - weeds
