Genetics and Adaptation

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Genetics and Adaptation

• Higher Biology
• Unit 2

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Variation

• Genes and Inheritance
• Shortly before a cell divides, the appearance of
  its nucleus changes. Long threads become visible
  in the nucleus, these are the chromosomes.

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• The number of chromosomes, and their size and
  shape varies between species.

Organism Number of Chromosomes
Human 46
Kangaroo 12
Domestic Chicken 36
Daisy 4
Hermit Crab 254
Dog 78
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• When viewed under the electron microscope, each
  chromosome is seen to consist of many dark bands.
• These are the genes, each of which is responsible
  for controlling one characteristic in an organism.

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Cell Division

• There are two types
• Mitosis (normal cell division in growing
  organisms)
• Meiosis (takes place in gamete mother cells in
  the sex organs to produce gametes).

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Mitosis

• This is simple cell division forming new cells
  (daughter cells) containing the same number of
  chromosomes as the mother cell.

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• In mitosis the number of chromosomes stays the
  same (46 in humans). This is called the diploid
  number.

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3
1
5
4
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Meiosis

• The genetic difference in gametes is the result
  of cell division in the sex cells called meiosis.
• During meiosis each diploid gamete mother cell
  undergoes two divisions to produce four haploid
  gametes.

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• The diploid number (2n) is the full chromosome
  number (complement) in normal cells.
• The haploid number (n) is half the diploid
  number. Only gametes have this number.

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• In a diploid cell, chromosomes can be sorted into
  pairs which look the same, and contain genes for
  the same characteristics.
• These pairs are called homologous pairs.
• Haploid gametes contain one member of each
  homologous pair.

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How meiosis increases variation

• Crossing over
• This takes place on the spindle during the first
  division of meiosis.
• Small pieces are exchanged between the
  chromosomes of a homologous pair.

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Chromatid
Centromere
Chiasma (crossing over point)
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• 2. Independent Assortment
• When homologous pairs of chromosomes line up at
  the equator of the spindle (during the first
  division of meiosis) the position of one pair is
  random in relation to any other pair.

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X
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MITOSIS MEIOSIS
Site of division Occurs all over the body In the sex organs
Pairing and movement of chromosomes Chromosomes replicate then pair up singly on the equator Homologous chromosomes form pairs Chromosomes line up in pairs on the equator
Exchange of genetic material Chiasmata not formed. No crossing over. Chiasmata formed, and crossing over occurs.
Number of divisions One division Two divisions
Number and type of cells produced 2 identical daughter cells 4 haploid gametes
Effect on chromosome number Stays the same Halved
Effect on variety Does not increase variation Increases variation
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Genetics

• Genetics is the study of patterns of inheritance
  from one generation to the next.

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Monohybrid cross

• Revision from Standard Grade/Int 2.

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Dihybrid Cross

• This is a cross involving the inheritance of two
  characteristics.
• In pea plants the seeds (peas) can be either
  round or wrinkled, and either yellow or green.
• Round and Yellow are the dominant alleles.

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• Round R
• Wrinkled r
• Yellow Y
• Green y
• Cross the true-breeding round yellow with the
  true breeding wrinkled green

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• To find the F2

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• Resulting phenotypes
• Round and yellow 9
• Round and green 3
• Wrinkled and yellow 3
• Wrinkled and green 1

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Linked genes

• If two genes are on the same chromosome they are
  said to be linked.
• Linked genes are transmitted together.

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• e.g. In peas, the gene for plant height and seed
  colour are on the same chromosome (i.e. they are
  linked)

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• T tall, t short, Y yellow, y green
• Tall Yellow X Short Green
• TT YY tt yy
• TY ty
• All offspring will be TALL and YELLOW

TY
ty TtYy
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• If two F1 plants are crossed
• TtYy x TtYy
• TY ty TY ty
• 3 Tall Yellow 1 Short Green

Only 2 types of gamete possible
TY ty
TY
ty
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• In reality, in the above cross, if 400 seeds grew
  from the F2 the ratio might be
• 292 7 6 95
• Tall Yellow Tall Green Short Yellow
  Short Green
• Recombinants

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• The Tall green and Short yellow plants are
  possible because of crossing over during meiosis.
• This can unlink linked genes. The new forms are
  called recombinants.

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Frequency of recombination

• Chiasmata can occur at any point along the length
  of homologous chromosomes.
• Genes that are further apart are more likely to
  be separated by crossing over than close genes.
  Recombinants gametes are therefore more likely to
  be formed.

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• The distance between a pair of linked genes is
  therefore indicated by the percentage number of
  F2 recombinants produced during a cross involving
  these genes.

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• This percentage is called the recombination
  frequency and is calculated as follows
• number of F2 recombinants
• COV x 100
• total number of F2 offspring

Recombination Frequency
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• In the example of the peas, the 400 F2 offspring
• 292 7 6 95
• Tall Yellow Tall Green Short Yellow
  Short Green
• Recombinants
• 13
• Recombination x 100 3.25
• Frequency 400

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Chromosome maps

• Chromosome maps are used to show the position of
  genes on a chromosomes relative to one another.
• A large recombination frequency means that genes
  are far apart a small frequency means that they
  are close together.

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• For example Crosses involving 4 linked genes
  (ABDE) gave the following Recombination
  frequencies

Genes Recombination Frequency
D x E 8
A x E 6
A x D 2
E x B 12
B x A 6
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• The positions of the genes on the chromosome are
  therefore as follows

E
B
D
A
2
6
6
12
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Sex Determination

• Diploid human body cells have 46 chromosomes.
• These are made up of 22 normal homologous pairs
  (called autosomes) and one pair of sex
  chromosomes.

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• The sex chromosomes in woman are two similar X
  chromosomes.
• In men there is one X chromosome and a smaller
  Y chromosome.
• XX XY

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• The X chromosomes carry many genes (unrelated
  to sex). The Y carries no genes.

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• In a man, the genes on the X chromosome have no
  allele on the Y.
• These are called sex-linked genes and will always
  express themselves.

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Inheritance of sex

• Woman Man
• XX XY
• X X X Y
• Ratio of 1 boy 1 girl

X X
X
Y
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Sex linkage

• A monohydrid cross involving a sex-linked gene
  does not give a typical 31 ratio in the F2
  generation.
• This is because the Y chromosome does not carry
  the sex-linked gene and therefore cannot provide
  dominance.

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• e.g. The gene for eye colour in Drosophilia flies
  is sex linked
• Red-eyed female X White-eyed male
• XRXR XrY
• XR Xr Y
• F1 red-eyed female 1
• red-eyed male 1

Xr Y
XR
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• White-eyed female X Red-eyed male
• XrXr XRY
• Xr XR Y
• F1 red-eyed female 1
• white-eyed male 1

XR Y
Xr
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Haemophilia

• Haemophilia is a disorder involving defective
  blood clotting.
• It is caused by a recessive gene on the X
  chromosome and is therefore sex-linked.

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• Queen Victoria was a carried of the gene (XHXh)
  and passed it onto many of her descendants in
  other European royal families

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Mutations

• Mutations
• Occurrence of mutations

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Mutagenic Agents
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Chromosome mutations

• Change in chromosome number

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Polyploidy
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Changes in chromosome structure
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Gene mutations

• Deletion
• Please stay where you are
• Please say where you are
• Cystic fibrosis is caused by a deletion of three
  nucleotides.

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• Inversion
• Guerrillas sending arms to aid rioters
• Guerrillas sending rams to aid rioters

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• Insertion

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• Substitution
• Flossie now arriving by air from new york
• Flossie not arriving by air from new york

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Karyotype

• A karyotype is a display of a complement of
  chromosomes showing their number, form and size.
• Non-disjunction of chromosome pair 21 leads to an
  extra copy of chromosome 21 in the embryo. This
  causes Downs Syndrome.

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• An example of duplication podcorn and popcorn.
• Relevant pair of alleles
• T (dominant) with husk
• t no husk
• At the locus (position) of this gene on the
  chromosome are 3 separate genes formed by a
  duplication mutation.

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• So
• T T
• T T will have complete husks
• T T
• and
• t t
• t t will have no husks
• t t

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But intermediates such as T T T t Will
have t t or T t partly T T T
t formed husks Duplication therefore
increased variation in this feature.
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So how did we get from life forming to modern
humans?
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Genesis Creation
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Evolution

• Evolution
• Evolution is a theory which states that the
  organisms alive today have arisen by a process of
  gradual change (over millions of years) from
  simple ancestors.

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Charles Darwin

• (1802 1882)
• Published the The Origin of the Species
• Introduced the idea of Natural Selection

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The mechanism of evolution

• The best explanation for evolution is provided by
  Darwins theory of Natural selection.

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Natural Selection

• Overproduction of offspring means that they
  cannot all survive, so there is
• Competition between the offspring

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• 3. Variation exists between the offspring because
  of
• Meiosis (independent assortment and crossing
  over)
• Mutation
• Fertilisation of gametes (a random process)

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• 4. Best suited offspring will survive longer and
  breed more
• 5. Favourable alleles will therefore be passed
  on, and increase in the population.

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Species and speciation

• A species is a group of organisms which have
  similar appearance and can interbreed to produce
  fertile offspring.
• They share the same range of genes, which are
  called the gene pool.

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Speciation

• Speciation is the formation of new species by
  natural selection.
• Speciation takes place when an existing species
  is split into two (or more) groups by a barrier
  which prevents interbreeding and exchange of
  genes.

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1. Single population
2. Barrier divides population
3. Accidental mutations occur in both halves of the
   population
4. Natural selection retains favourable mutations
5. Each half of the population evolves differently
6. Two species have evolved

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• Barriers may be
• Ecological
• Geographical
• Reproductive

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(a) Ecological barriers

• These might be caused by rainfall, temperature,
  soil pH etc.
• e.g. The effect of temperature on a population of
  alpine plants

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(b) Geographical barriers

• These include sea, rivers, deserts, mountains.
• e.g. The effect of a mountain range on a
  population of tiger beetles.

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(c) Reproductive barriers

• These might include
• Changes in courtship patterns
• Changes in breeding seasons
• which can result in one part of a population
  being unable to breed with one another.

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Adaptive radiation

• Adaptive radiation has taken place when several
  different species have evolved from one common
  ancestor.
• This might happen when a feature of an organism
  evolves to fill a number of different niches.

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• An organisms niche is the precise way in which
  it fits into its environment.
• Adaptive radiation is shown well by the beak
  shapes of Darwins Finches on the Galapagos
  Islands.

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• This process is well shown by Darwins finches
  on the Galapagos Islands.

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Darwins Finches
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• Make your own notes of adaptative radiation from
  Torrance

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High speed evolution

• Evolution normally takes place very slowly, but
  occasionally can be seen taking place much more
  rapidly. This is high speed evolution.
• Two examples are
• Melanic Peppered moths
• Antibiotic resistant bacteria

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• Make your own notes of this topic from Torrance

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• 2. Resistance to antibiotics

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Extinction of species

• As evolution proceeds new and better-adapted
  species evolve.
• Natural selection results in the disappearance
  (extinction) of their ancestors.

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• The natural (slow) rate of species extinction has
  recently been greatly accelerated by mans
  activities.

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Main threats

• 1. Over-hunting

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• 2. Habitat destruction

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Conservation of species

• Genetic diversity (variety) is essential for
  natural selection.
• It is also important for selective breeding of
  organisms under mans control.

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• Man uses a variety of methods to ensure this
  genetic diversity is maintained
• Wildlife reserves
• Captive breeding
• Cell banks

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1. Wildlife reserves are natural areas where habitat
   is managed and protected for the benefit of rare
   species

RSPB Reserve at Culbin Sands. Ngorongoro Crater,
Tanzania
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• Captive breeding involves taking animals from the
  wild and breeding them in secure conditions until
  they can be re-introduced to their natural
  habitat.

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1. Cell and seed banks contain collections of living
   gametes or seeds which can be preserved in
   controlled temperature and humidity.

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Artificial Selection

• Artificial selection is the deliberate selection
  by humans of organisms with characteristics
  useful to mankind.

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• Selective breeding
• Desirable features (perhaps not successful in the
  wild) are selected by man, and organisms showing
  these features are bred together.

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• (i) Wild Cabbage

Common ancestor Wild Sea Cabbage
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• (ii) Dogs

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• (b) Inbreeding and hybridisation
• Inbreeding Breeding is allowed between two
  individuals possessing a desirable feature.
• Advantages Next generation retains desired
  feature.
• Disadvantages Increased chance of offspring
  which are homozygous recessive for a harmful
  allele.

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• Hybridisation Breeding between two genetically
  different varieties of the same species.
• Superior offspring may be produced by combining
  the good features of two parents. This is hybrid
  vigour.
• Heterozygous offspring will have harmful
  recessive alleles masked by the dominant allele.

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• (c) Genetic engineering
• This is the creation, by man, of new combinations
  of genes from more than one species.
• It involves the transfer of genes from the genome
  (haploid gene set) of one organism (e.g. Human)
  to the genome of another organism (e.g.
  Bacterium).

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• Two stages are involved
• Locating the genes
• Transferring the genes

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1. Locating the gene

• Four methods exist
• Chromosome mapping using cross over values of
  linked genes.
• Chromosome banding patterns
• Irradiation of chromosomes (resulting in gene
  deletion mutations) can be followed by genetic
  crosses to identify unusual offspring
  characteristics.

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• 3. Gene probes
• Take the protein (e.g. Hormone or enzyme) and
  identify the amino acid sequence. The base
  sequence of the genetic code can then be worked
  out.
• Make single stranded DNA with the identified
  bases. This is the gene probe, It is labelled
  radioactively.

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A T G C C T A C G T T G
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• Select the relevant chromosome from the nucleus
  and break it into fragments.
• Mix probe and fragments. The probe attaches to
  the fragment carrying the required gene.

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• (4) Genome sequencing (Human Genome Project)
• The entire human genome has been sequenced
  which means the order of the bases are known.
  Computer programmes can then be used to identify
  the position of genes based on their similarity
  to known genes in other organisms.

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2. Transferring the gene

• Once located, the gene is cut from the chromosome
  using the enzyme endonuclease,
• The gene is then inserted into a bacterial
  plasmid (small circular chromosome) using the
  enzyme ligase.

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Human DNA
Endonuclease site
Cut with endonuclease
Cut with endonuclease
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An application of this technology

• The gene for the human insulin protein can be
  inserted into the bacterium E. coli (Escherichia
  coli).
• The bacteria containing the plasmid are then
  grown in large numbers and made to express
  (produce) the insulin protein which can then be
  purified.

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(d) Somatic Fusion

• This technique is used to produce new, improved
  crop species.
• Two different species cannot interbreed
  successfully. At best a cross between them will
  produce a sterile hybrid.
• However new techniques are enabling scientists to
  overcome this problem of sexual incompatibility.

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1. Suitable cells from two plant species are
   selected.
2. The cells walls are digested away using
   cellulase. Forming a protoplast.
3. Somatic fusion induced by electric current.
   Forming a somatic cell hydrid.

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• Cell wall formation is induced.
• Cell division occurs producing a mass of
  un-differentiated cells.
• Cells treated with hormones to produced a hybrid
  plant.

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Animal and Plant Adaptations

• Higher Biology

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This section covers

• Water balance in plants
• Water balance in animals
• How animals obtain food
• Living in social groups

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Water balance in plants

• Revision from S-Grade

??? ??? sop.hyll ??? ??? mesophyll ,
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Transpiration

• Transpiration is the loss of water by evaporation
  from the leaves of a plant.
• The transpiration stream is the flow of water up
  through the plant from the roots to the leaves.

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Evidence for transpiration

• A ____________ plant was put in a bag with a
  humidity sensor.
• The experiment proved that transpiration happens
  as the humidity in the bag with the plant was
  greater than the humidity of the room.

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The rate of transpiration

• Over a period of _____ hours the plant has lost
  ________ of water which represents a rate of loss
  of ______ ml/hour.

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Comparing transpiration rates

• Transpiration can be measured using a potometer.

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• The plant was then subjected to normal
  conditions, windy conditions and more humid
  conditions.
• The windy conditions were generated using a fan.
• The humid conditions were created by a bag.

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Factors affecting the rate of transpiration

• Wind

Transpiration Rate
Wind speed
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• Explanation Wind blows water vapour as it leaves
  the leaf. Therefore a steep concentration
  gradient exists between the inside and outside of
  the leaf. Leading to rapid diffusion.

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• 2. Humidity

Transpiration Rate
Humidity
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• Explanation High concentration of water
  molecules in air outside leads to a small
  concentration gradient. Therefore diffusion is
  slow.

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• 3. Temperature
• Explanation Water evaporates from liquid to
  vapour more quickly.

Transpiration Rate
Temperature
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• 4. Light
• Explanation Stomata are closed in darkness and
  open gradually as light levels rise.

Transpiration Rate
Light
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• In summary, transpiration is increased by
• Increase in wind speed
• Decrease in humidity
• Increase in temperature
• Increase in light intensity.

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Stomata

• Stomata (stoma singular) are found in the lower
  epidermis of the leaf.

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• Purpose Allow entry of carbon dioxide for
  photosynthesis.
• Problem Water vapour escapes from the leaf
  through the pore.
• Mechanisms to reduce water loss
• Stomata are on underside of leaf (cool and
  shaded)
• Stomata close in darkness (no need for carbon
  dioxide)

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How stomata open

• The opening of stomata depends on the turgor of
  the guard cells.
• If they are turgid (much water in them) then the
  pore opens.
• If they are flaccid (water has moved out) then
  the pore closes.

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The transpiration stream

• This is the flow of water through a plant from
  the root to the leaves.
• It replaces the losses due to transpiration.

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• Other benefits are
• Minerals (nutrient ions) are transported in
  solution in the water.
• Evaporation of water cools the plants leaves.

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1. How water enters the root

• Water enters root hair cells on the root
  epidermis.
• Root hairs provide a large surface area for water
  uptake.

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A
C
B
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• Water enters the root and crosses the cortex to
  the xylem in two ways
• Soaking along the cell walls of the cortex cells.

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• 2. By osmosis. Soil water has a higher water
  concentration than the cytoplasm of the root hair
  cell (Cell A). Water therefore enters the cell by
  osmosis.
• Cell A now has a higher water concentration than
  Cell B, so water moves from A in to B, and so on
  till it reaches the xylem.

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2. How water moves up the xylem

• Root pressure
• The force with which water crosses the root and
  enters the xylem by osmosis is enough to push
  water a short distance up the xylem vessels.

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• (b) Capillarity
• Water rises up the inside of a thin xylem tube
  because of adhesion between water molecules and
  the wall of the tube.

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• (c) Transpiration pull

D
C
B
A
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• As water evaporates from the leaves it creates a
  tension (pulling force).
• Cohesion forces between water molecules mean that
  they will attract each other and so the tension
  pulls the water column up the xylem vessel.

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Adaptations to environmental conditions

• Mesophytes are normal plants which grow where
  water is easily available and excessive
  transpiration is not a problem (e.g. Dandelion,
  buttercup).

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Specialised plants

• 1. Xerophytes are plants which are adapted for
  life in habitats where the transpiration rate is
  high and/or water is hard to get
• e.g. Hot, dry deserts cacti
• Exposed, windy hills - heather

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Adaptation Explanation
Fewer stomata Reduces water loss
Thick leaf cuticle Prevents evaporation through the cuticle
Rolled or hairy leaves Humid air builds up outside the stomata
Stomata sunken in pits Humid air builds up outside the stomata
Deep roots Find water deep underground
Widespread surface roots Gather maximum rain after a shower
Succulent tissues Store water
Short life cycle Survive dry conditions as a seed
Reversed stomatal rhythm Open at night when its cool, close during the hot day
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• 2. Hydrophytes are plants which live partly or
  totally submerged in water (e.g. Pondweed, water
  lily).
• They show the following adaptations

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• Air spaces
• Possesses an extensive system of air-filled
  cavities. Instead of escaping into the
  surrounding water, much of the oxygen is stored
  in these spaces and used for respiration when
  required.

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• The presence of such aerated tissue also gives a
  submerged plant buoyancy keeping its leaves near
  the surface for light.

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• Reduction of xylem
• Any xylem present is normally found at the centre
  of the stem. This allows the stem maximum
  flexibility in response to water movements while
  at the same time enabling it to resist pulling
  strains.

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• Specialised leaves
• A hydrophytes submerged leaves are narrow in
  shape or finely divided. This helps them avoid
  being torn by water currents.

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Water balance in animals

• Osmoregulation is the process by which animals
  keep the water concentration of their body fluids
  constant.

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1.
2.
4.
3.
In groups discuss the structure of the kidney.
(1) Identify the numbered structures. (2) Be able
to describe exactly what happens in each of the
numbered structures. (3) What is filtered out of
the blood? (4) What is reabsorbed? One person
from the class will be expected to stand at the
board and describe the function of the kidney
so be sure every in the group knows what they are
talking about.
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1. Osmoregulation in freshwater fish

• e.g. Trout
• Problem The tissues of the fish are hypertonic
  (lower water concentration) to the river water.
• Water therefore enters by osmosis through the
  gills and intestines.

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• Solution
• Many large glomeruli in kidney
• High filtration rate of blood
• Large volume of dilute urine
• Chloride secretory cells in the gills absorb
  salts from water by active transport.

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2. Osmoregulation in saltwater fish

• e.g. Cod
• Problem Sea water is hypertonic to the tissues
  of the fish, so the fish loses water by osmosis.

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• Solution
• Sea water is drunk.
• Chloride secretory cells excrete salt.
• Few, small glomeruli in kidney
• Low filtration rate.
• small volume of concentrated urine.

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3. Adaptations of migratory fish

• e.g. Salmon or eels
• Make your own notes from p172 Q3 (a) and (b)

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4. Water conservation by desert rats

• Problem Since there is little rainfall in the
  desert and high daytime temperatures (with low
  night time temperatures) desert mammals, such as
  the kangaroo rat, have only a limited supply of
  water available to them.

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• To survive they have to be able to practise
  rigorous water conservation.
• Obtaining water In its natural habitat, the
  kangaroo rat does not drink water at all. It is
  able to obtain all its water from its food (dry
  seeds) and remain in water balance as the
  following diagram shows

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Ways of conserving water

• Physiological adaptations
• Mouth and nasal passages tend to be dry, thereby
  reducing water loss during expiration.
• Bloodstream contains a high level of
  anti-diuretic hormone.

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• Kidney tubules possess very long loops of Henle
  (kidney tubules). These adaptations promote water
  reabsorption so effectively that it can produce
  urine 17 times more concentrated than its blood.

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• It does not sweat.
• Its large intestine is extremely efficient at
  reabsorbing water from waste material and
  producing faeces with a very low water content.

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• Behavioural adaptations
• Remains in its underground burrow during the
  extreme heat of the day.
• Inside the burrow the air is cooler and more
  humid. Thus the air being inhaled by the rat is
  almost as damp as the air being exhaled and
  minimum water loss occurs.
• It has no need to produce sweat as it is active
  at night.

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Obtaining food

• Most animals are mobile and actively search for
  and/or pursue food.
• A few animals (e.g. Barnacles) are sessile (fixed
  in one place) and depend on filtering food from
  water.

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Forms of nutrition

• Auxotrophic nutrition is used only by green
  plants.
• They employ photosynthesis to make complex
  organic substances from simple inorganic
  molecules.

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• 2. Heterotrophic nutrition is used by animals and
  fungi.
• They depend on plants for ready-made organic
  materials.

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Foraging for food

• When animals go foraging for food, they show
  distinct behaviour patterns organised to gain
  maximum energy.

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Foraging behaviour in colonial insects

• Bees
• When a worker bee locates a good source of food
  it returns to the hive and dances. This gives
  information on the location of the food to other
  workers.
• Bee clip

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• (b) Ants
• Use pg 190 of text-book to make notes.
• Make a copy of the diagram on pg 190.

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Economics of foraging behaviour

• Net loss of energy will result if the energy
  obtained from an animals food is less than the
  energy spent foraging for it.
• Animals must consume food items which give them
  the best return for time and energy spent.
• Three factors affect this

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• (a) Time

Predator Prey Search Pursuit Time Economics
Lion Zebra Short time Long time Must spend time selecting an old or weak individual
Ant-eater Ant Long time None Cannot afford time to be selective all ants eaten
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• (b) Quality of the food
• Worst quality food is found very quickly but the
  energy reward is poor.
• Best quality food takes a long time to find but
  the energy reward is high.
• Intermediate quality food doesnt take too long
  to find and has a reasonably good energy reward
  this is the optimum energy value approach in a
  poor ecosystem.

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• (c) Size of prey items
• Small prey items require little energy to find
  and kill, but contain little energy reward.
• Large prey items require a lot of energy to find
  and kill, and contain a large energy reward.
• Medium sized prey items dont require too much
  energy to find and kill, and contain a reasonably
  good energy reward this is the optimum energy
  value approach.

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Competition

• If resources are scarce, animals may compete for
• food
• water
• space
• shelter
• mates

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Types of competition

• Interspecific competition takes place between
  members of different species.
• For example, English Crayfish are being
  exterminated from English rivers by introduced
  American Crayfish.

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• Intraspecific competition takes place between
  members of the same species.
• This is more intense because the animals have
  identical requirements and are also competing for
  mates.
• For example, Red deer stags compete fiercely for
  females during the autumn rut.

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• Competition often leads to adaptations which
  ensure the survival of the fittest individuals.

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Living in social groups

• Dominance heirarchy (e.g. peck order among hens)
• In a dominance hierarchy animals organise
  themselves in an order from strongest to weakest.
  This order is maintained largely by threat.

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• Benefits are
• Survival of the fittest individuals are ensured.
• Experienced leadership is guaranteed.
• Little fighting takes place, so injury is avoided
  and energy is saved.

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• Individuals often display behaviours to indicate
  dominance or submission.

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2) Co-operative hunting

• Some predatory mammals, such as killer whales,
  lions, wolves and wild dogs, rely on co-operation
  between members of the social group to hunt their
  prey.

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• Ambush strategy
• Employed by lions involves some predators driving
  prey towards others that are hidden in cover and
  ready to pounce.
• Running down
• Dogs and wolves take turns at running down a
  solitary prey animal to the point of exhaustion
  and then attack it.

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Advantages of co-operative hunting

• More effective hunting strategies can be employed
• A group can kill larger prey than a lone
  individual
• Weaker individuals will get some food

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• Food sharing will only occur if the reward for
  sharing exceeds the reward for foraging
  individually.

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Territorial behaviour

• A defended territory provides food for an animal,
  its mate and its offspring.
• Factors affecting territory size
• Large enough to supply requirements
• Small enough to defend effectively
• Larger when food is in short supply than when
  food is plentiful.

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• The energy gained from the food in the territory
  must exceed the energy needed to defend it.

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Obtaining Food - Plants

• Unlike animals, which are mainly mobile, plants
  are sessile, which means they cannot move around.
• Plants must therefore obtain their food, water
  and minerals from the soil and air around them.

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Competition between plants

• Plants compete for
• Water
• Light
• Soil minerals

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• Plants of same species often grow together, so
  competition is intraspecific and therefore
  intense.

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Compensation Point

• This is the level of light intensity at which the
  rates of photosynthesis and respiration are
  equal.
• The plant is making and using carbohydrate at the
  same rate.

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Rate of Process
Midnight Midday Midnight
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Sun and shade plants

• Sun plants (e.g. Dandelion) live only in bright
  habitats. They achieve the compensation point
  slowly but go on to photosynthesise very rapidly
  later in the day.

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• Shade plants (e.g. Primrose, Wood Anemone) live
  in shady places. They achieve compensation point
  very rapidly but never receive enough light for a
  fast rate of
• photosynthesis later in
• the day.

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Coping with dangers

• Plants
• Ability to tolerate grazing by herbivores
• Plants can tolerate grazing if
• Low growing points

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• Leaves flat to the ground
• The ability to regenerate missing parts

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Effect of grazing on species diversity
Least intense
Most intense
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• No grazing Vigorous grasses thrive and shade out
  most wild flowers which cannot survive the
  competition.
• Heavy grazing Grasses and wild flowers are
  eaten. Only plants which grow from the base
  (grass, daisy) can survive.
• Moderate grazing Vigorous grasses are kept in
  check and a good variety of wild flowers can grow.

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Plant defences

• Chemical defences
• Stings (e.g. nettles). Each sting hair takes the
  form of a thin capillary tube ending in a
  spherical tip.
• When an animal touches a hair, its tip breaks off
  leaving a sharp edge. This penetrates the skin
  allowing the liquid irritant to be injected into
  the animal.

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• (b) Cyanogenesis (e.g. Clover)
• Hydrogen cyanide is produced in clover leaves in
  response to being nibbled by slugs. It is formed
  by an enzyme acting on a non-toxic chemical
  called glycoside.

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• (2) Physical defences
• Thorns a thorn is a sharp side branch.
• Spines a spine is a sharp pointed leaf.

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Animal defences

• Avoidance behaviour is an instinctive response
  by an animal to avoid danger e.g.
• Running away
• With drawing into a shell
• Hiding in a burrow

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Habituation

• Habituation is a short term change in behaviour
  when an animal stops responding to a stimulus
  which is proving harmless.

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• This
• Allows the animal to keep feeding
• Conserves energy
• Is specific to one stimulus
• Habituation is temporary. After a short time the
  original avoidance behaviour will return.

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• Fan worms are stimulated by shadows as they are
  the prey of fish, but if it is sea weed floating
  on the surface the worm will retreat back into
  its tube, but if it continues and proves harmless
  it will stop retreating for a short time.

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Learning to avoid danger

• Learning involves a long term modification of an
  animals behaviour. In order to learn something
  you need to be able to remember.

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1. Learning to avoid poisonous food

• Pupil notes from Torrance Pg 211-212 on Toad and
  Bee example.

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2. IMPRINTING
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• Newly hatched ducklings and goslings quickly
  learn to follow the first large object they see
  if it moves and makes sounds normally this
  would be their mother.

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• This can only happen during a brief period of
  early life and is called imprinting.
• It is a behavioural adaptation of survival value
  because it provides a mean by which they can
  avoid danger.
• Ducklings can become wrongly imprinted on humans
  if they are the first things they see.

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Animal defence mechanisms - individuals
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ACTIVE DEFENCEPhysical

• Claws and teeth

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ACTIVE DEFENCE - Chemical
247
ACTIVE DEFENCEBehaviour

• Feigning death
• Intimidation

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PASSIVE DEFENCE

• Protective covering
• of spines

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PASSIVE DEFENCEProtective covering

• Shells

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PASSIVE DEFENCECamouflage

• Colour and Shape

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PASSIVE DEFENCE Warning colouration
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PASSIVE DEFENCEMimicry

• Pretending to
• be nastier than
• you are

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Animal defence mechanisms - groups

• Pupil note from Torrance Pg 215 216 on Musk Ox,
  Quail Baboon.