Download Module B1a, topic 1 Food chains eg grass → rabbit → fox producer

Module B1a, topic 1
Food chains
eg grass
producer
→
rabbit
primary consumer
prey
herbivore
→
fox
secondary consumer
predator
carnivore
Food webs
eg
If spiders increase - herbivorous insects decrease, insectivorous birds increase etc
Interspecies competition : two creatures from different species compete for food and
space
Intraspecies competition : two creatures of the same species compete for food and space
Pyramids of number
eg
A couple of raptors eat half a dozen birds which eat hundreds of invertebrates which feed
on one willow tree
Pyramids of biomass
eg
As you move up the pyramid of biomass, energy is lost through processes of respiration,
growing, waste products (such as faeces and urine), heat energy, movement, etc.
Therefore less and less energy is available to the next trophic level. So more must be
consumed from the lower trophic level to gain the relative amount of energy.
Food production
Plants convert 1% of solar energy into chemical energy.
Cows pass on about 10% of that 1% ( 33% lost in movement of the cow, 57% lost in
excretion )
so it is more cost effective to produce a field of wheat than keep a field of cows
Intensive ( factory ) farming improves efficiency as it reduces movement
Organic farming avoids the use of fertilisers and pesticides
Classsification of living things
Linnaeus : according to what things look like and Darwin : according to evolution
Each living thing has two latin names : Genus species
Capital letter lower case letter
eg : Camelus bactrianus ( bactrian camel having two humps )
Camelus dromedaries ( dromedary camel having one hump )
Classification begins with 5 kingdoms : monera, protista, fungi, plants, animals
The complete classification applied to animals :Kingdom
: Animal
Phylum
: Chordata ( bilaterally symmetrical bodies )
Subphylum : Vertebrate ( backbone )
Class
: Mammal
Order
: Primate
Genus
: Homo
Species
: sapiens
Darwin’s theory of evolution
states that evolution happens by natural selection
• Individuals in a species show a wide range of variation
• Because of differences in genes
• Individuals most suited to their environment are more likely to survive and reproduce
• The genes that allowed them to be successful are passed to their offspring
• Individuals that are poorly adapted to their environment are less likely to survive and may
become extinct
Fossils are good evidence for this as they show how organisms have changed over time
Selective breeding / artificial selection
is the process of breeding plants or animals for particular genetic traits. Typically, strains
which
are selectively bred are domesticated ( eg dogs ). Bred animals are known as breeds while
bred
plants are known as varieties, cultigens or cultivars. A cross of animals results in what is
called a
crossbreed ( eg mule = male donkey + female horse ) and crossbred plants are called
hybrids
( eg loganberry = raspberry + blackberry )
Genetic engineering
the direct manipulation of an organism’s genes.
eg the manufacture of synthetic human insulin through the use of modified bacteria
Module B1a, topic 2
A gene is a portion of DNA which holds the information to build and maintain an
organism's cells and pass genetic traits ( eye colour, blood type, skin colour ) to offspring
The total complement of genes in an organism or cell is known as its genome which may
be stored on one or more chromosomes found in the nucleus of the organisms cells.
Gene → DNA → Chromosome → Nucleus
↓
Human beings have 46 chromosomes arranged in 23 pairs - the human karyotype
diploid number
There are two versions of every gene, one on each chromosome in a pair, called alleles
Cell division called mitosis produces two cells which are genetically identical
Cell division called meiosis, which occurs in the sex cells ( gametes ), produces only one
chromosome from each pair so 23 in total
haploid number
Genes were first suggested by Gregor Mendel who experimented with the breeding of
sweet pea plants.
James Watson and Francis Crick used x-ray diffraction data collected by Rosalind Franklin
to work out the double helix structure of DNA in 1953.
The Human Genome Project ( from 1990 James Watson ) finally mapped the 20000 genes
of the human genome.
Sexual reproduction ( involves fertilisation of an egg by sperm ) results in offspring having
traits of both parents leading to variation
Asexual reproduction ( possible in plants ) results in genetically identical offspring – clones
Transgenic organisms are organisms that have DNA inserted into them from another
species.
The process enables, for example, milk to be produced containing human antibodies or low
cholesterol
Alleles are different forms of the same gene.
Someone having blue eyes would have two blue alleles.
If someone has one blue allele and one brown allele then their eyes will be brown because
brown alleles are dominant ( blue alleles are recessive )
Capital letter
lower case letter
Heterozygous refers to two alleles which are different.
Homozygous refers to two alleles that are the same.
Genetics diagrams
Mother
genotype C
C
C CC
Mother
C
c
CC
Father
c
Cc
cc
Cc
cc
Father
C
Cc
Cc
50% chance of offspring being CC
50% chance of offspring being Cc
c
50% chance of offspring being Cc
50% chance of offspring being cc
Inherited characteristics can be modified by environmental conditions
eg poor diet can reduce growth so offspring from two tall parents won’t necessarily be tall