Biology Paper 2 (HM)

What do organisms compete for

• Food

• Water

• Space

• Light

• CO2/O2

• Mate

Interdependance

Organisms depending on each other for survival. Leads to the creation of a community.

Abiotic factors

Non living factors

• Light

• Temperature

• Moisture

• Soil pH

• CO2 & O2 consentration

Biotic factors

Impact of other organisms on an ecosystem

• Food

• Predators/prey

• Pathogens

Sampling

• Place QUADRAT in random positions in area (ideally 10% of area, using random number generator to choose locations)

• Count number of chosen organism in each, calculate mean then multiply by total area to get estimate for population.

• Moving it along a transect allows you to observe changes in population density over a distance

Food chains

Show the direction of biomass transfer between organisms

What is A?

Producer (Produces biomass)

What is B?

Primary consumer(Herbivore/omnivore)

What is C?

Secondary consumer (Carnivore/omnivore)

What is D?

Tertiary consumer (Carnivore/Omnivore)

Apex predator

• Always at the top of food chains

• Have no natural predator

Populations fluctuate over time because …

• Because food supply, predators, and competition change at different trophic levels.

• When one trophic level rises or falls, the levels above and below it react.

A pyramid of biomass

Indicates how much biomass is transferred between trophic levels

How much energy is lost when moving up a trophic level

10%

Why is energy lost when moving up trophic levels?

• Organisms dont normally eat every part

• Non-edible parts are lost to feases

• Most of the nutrients that animals absorb used to release energy through respiration

How to calculate efficiency of biomass transfer (%)

100 x (Biomass transferred to next level / Biomass that was available at the previous level)

Decomposition conditions

Higher temperature and higher humidity increase the rate of decomposition.

A:

Evaporation

B:

Rain precipitation

C:

Runs into rivers/sea

Biodiversity

• The variety of species of organisms that exist in an ecosystem

• High biodiversity creates a stable ecosystem as organisms will be be able to be dependant on greater number of species for survival

Human developement

• usually results in reduced biodiversity, due to destruction of habitats

• Disposing of waste in safe ways in order to reduce our impact is getting harder.

We need land to..

• buildings/shelter

• quarrying

• farming

• waste disposal

Why are peat bogs are being destroyed

• To make compost

• This reduces biodiversity of that ecosystem

• Burning peat releases CO2 (Global warming)

Deforestation

• Reduce biodiversity

• Usually to create farmland

Animal and plant reproduction (Type)

• Animals - Sexually

• Plants - Sexually & Asexually

Asexual reproduction process uses …

mitosis meaning offspring will be identical

Sexual reproduction advantage

Offspring can become become better (Adaption)

Asexual advantage

only 1 organism needed to reproduce

Genome

entire genetic code of an organism

DNA

double helix polymer that stores genetic code

Gene

portion of DNA that codes for a protein

Genotype

an organism specific genetic code

Phenotype

Physical characteristics expressed by the genetic code

Inheritance

• Characteristics are shaped by the types and quantities of proteins produced.

• Most characteristics are the result of multiple genes interacting.

• Different versions of the same gene are known as alleles.

• Some characteristics are controlled by a single gene.

Dominant alleles

• expressed even when genotype contains a RECESSIVE allele

• There must be no dominant allele in order for a recessive allele to be expressed in the phenotype.

Male/Female chromosome

• Men - XY

• Women - XX

Variation is a result of

genetic and environmental factors

Darwin’s theory of evolution

• Random mutations results in variation

• Some organisms better adapted to environment

• These compete ('survival of the fittest')

• Those better adapted are more likely to survive; over time these desirable characteristics are more pronounced.

LAMARCK'S THEORY OF EVOLUTION

Mutations/adaptations are a result of environment affecting characteristics inherited by offspring; not random.

How is ANTIBIOTIC-RESISTANT BACTERIA used as evidence for Darwinian evolution

If not all bacteria killed, those most resistant will reproduce. This is why you must complete the full course of antibiotics.

Selective breeding

Breeding organisms that have desired characteristics to produce offspring in which they are more pronounced

Species

A group of organisms that are capable of producing fertile offspring

Genetic engineering

The INSERTION of a GENE into an ORGANISM'S GENOME so it SYNTHESISES a specific PROTEIN to achieve a DESIRED CHARACTERISTIC.

Genetic engineering process

1. Desired gene is cut from another organisms DNA using restriction enzymes, leaving it with sticky ends

2. Gene inserted into a vector (e.g bacteria plasmid)

3. Vector inserts gene into cells of another organism early in development

4. Organism develops with desired characteristics

Cloning

• Producing genetically identical organisms

• You can clone plants using cuttings or tissue cultures

• Cells from fertilisation can be separated to produce identical offspring

Cloning process

1. Nucleus taken from skin cell of organism to be cloned

2. Nucleus inserted into an egg cell

3. Electric shock causes cell to split and develop

4. Developing cells inserted into surrogate mother