Download of species diversity

Specie diversity and human activities
• Compare the meaning of the terms species biodiversity
and species richness.
• Explain why it is useful for ecologists to calculate a
species diversity index.
• Compare the index of species diversity in natural and
agricultural ecosystems. Explain the differences.
• Summarise the changes in farm practises in the last 40
years and the movement towards intensive farming.
• Describe management techniques that farmers can use
to try and increase species and habitat diversity
without raising food costs or lowering yields.
Answers
•
Species diversity= no of diff species and no of individuals of each species within a
community
Species richness= no of diff species in a particular area at a given time- takes no
account of the number (abundance) of individuals
• quantitative- provides a number that makes it easier to compare the variety in
different habitats
•
natural
agricultural
explanation
Many individuals of
a large number of
different specieshigh index of
diversity
Many individuals of
a small number of
one species
Other species
compete for small
space and
resources.
Low index of
diversity
Agricultural ecosystems controlled
by humans.
Farmers select one species with
desirable characteristic
Pesticides are used to exclude other
species (so that they do not compete
with farmed species)
Changes in farm practises in last 40 years:
Move to intensive farming
Food production doubled
How?
Improved genetic varieties
Greater use of chemical fertilisers and pesticides
Greater use of biotechnology
Larger farms
Conversion of land supporting natural communities into farmland e.g removal of
hedgerows, creation of monocultures, filling in ponds
Over grazing of land
Lack of crop rotation/ intercropping
Management techniques for conservation:
Maintain A shape hedgerows
Leave wet corners of fields
Plant hedges as field
boundaries
Reduce use of pesticides – use
biological control
Maintain existing ponds
Use organic fertilisers
Tasks
• Species diversity and human activities
research/ notes should be completed
• Species diversity and human activities exam
questions should be completed
• All notes and summary questions for chapter
10 up to 10.3 should be completed.
Investigating Diversity
Learning Objective:
In order to be successful in this lesson you must
be able to:
evaluate direct DNA/protein sequencing against methods of
measuring the frequency of characteristics.
Investigating diversity
explain how
DNA
hybridisation
and
biochemical
analysis can be
used to suggest
relationships
between
different
organisms
within/between
species
interpret data
relating to
DNA hybridisation
or biochemical
analysis
PROGRESS
evaluate direct
DNA/protein
sequencing
against methods
of measuring the
frequency of
characteristics.
Evidence for classification
Classification – originally based
on observable features.
We now know that:
• DNA determines the
proteins of an organism.
• Proteins determine the
features of an organism.
Hence changes in the feature
of an organism are due to
changes in it’s DNA.
Comparing the genetic diversity within and
between different species help scientists to
determine the evolutionary relationships
between them.
Comparing genetic diversity through observable
characteristics :
• Each observable characteristic is determined by genes (with
environmental influences)
• Variety within a characteristic depends on the number and
variety of alleles of that gene (plus environmental differences)
Limitations:
A large number of characteristics are coded for by more than one gene (polygene). They
vary continuously so it is difficult to distinguish one from another.
Advances in
Environmental factors alter characteristics.
technology
now allow us to
use more
accurate
methods to
measure
species
diversity.
New methods of comparing genetic
diversity and determining evolutionary
relationships
Comparing DNA and mRNA base
sequences
Comparing amino acid sequences
in proteins
Immunological comparisons of
proteins
DNA hybridisation
Comparison of DNA base sequences
The DNA of organisms can be directly compared
by looking at the order of bases in each.
Closely related species will have a higher
percentage of similarities in their DNA base
order.
Humans and chimps share 94%
Humans and mice share 85%
Comparison of DNA base sequences
• During evolution one species
gives rise to another, the
DNA of the new species will
initially be very similar.
• Due to mutations the
sequences of nucleotide
bases in DNA changes.
• Over time the new species
will accumulate more
differences in its DNA.
• Therefore we would expect
species that are more closely
related to have more
similarities in their DNA.
You need to be able to explain how gene technology has changed the
way in which relationships between organisms are worked out
Use your textbook to describe how DNA
sequencing is carried out.
Extension
reading:
blog
Computer screen
display of DNA
sequencing
pattern
http://www.hhmi.org/biointeractive/creating-phylogenetic-trees-dna-sequences
DNA hybridisation
DNA hybridisation is used to see how
similar DNA is without sequencing it.
Labelled using
radioactive or
fluorescent marker
Closely related species –
more base pairing,
more hydrogen bonds formed,
higher temperature required to separate them
Distantly related species –
few bases pair up
less hydrogen bonds formed
lower temperature required to separate them
http://highered.mheducation.com/sites/0072556781/studen
t_view0/chapter14/animation_quiz_4.html
Comparison of the base sequence of
mRNA
The base sequences on
mRNA are
complementary to those
on the strand of DNA
from which they were
made.
Therefore, we can measure
DNA diversity and genetic
diversity by comparing
the sequence of bases of
mRNA.
Comparison of proteins
Similar organisms will have similar protein in their cells.
Proteins can be compared in two ways:
Comparison of amino acid sequences
• The sequence of amino acids in proteins is
determined by DNA.
• The degree of similarity in the amino acid
sequence of the same protein in two species will
therefore determine how closely related they are.
Comparison of amino acid sequences
Species A
Val
Ser
Phe
Ser
Species B
Val
Ser
Phe
Phe
Species C
Phe
Glu
Val
Glu
The amino acid sequence of species A and B are very similar.
The sequence from species C is very different from the others.
This would suggest that species A and B are more closely related.
Immunological comparisons
Antibodies of one species will respond to specific
antigens on proteins, such as albumin, in the blood
serum of another.
Species A
Human
Blood serum Albumin
(antigens)
serum injected
serum added to
another species
Species C
Antibodies bind to corresponding
antigens on albumen of species C
producing a precipitate.
Species B
Rabbit
Produces antibodies in
response to the antigen from
species A
The greater the number
of similar antigens ,
• the more precipitate
formed,
• the more closely related
the species is.
• Scientists investigated the
effect of hunting on the
genetic diversity of
otters. Otters are animals
that were killed in very
large numbers for their
fur in the past.
• The scientists obtained
DNA from otters alive
today and otters that
were alive before hunting
started.
• For each sample of DNA,
they recorded the
number of base pairs in
alleles of the same gene.
Mutations change the
numbers of base pairs
over time.
The scientists obtained DNA from otters that were alive before hunting started.
Suggest one source of this DNA.
[1 mark]
What can you conclude about the effect of hunting on genetic diversity in otters? Use data
from Figure 6 to support your answer.
[2 marks]
• Bone/skin/preserved remains / museums;
1
• 1. (Hunting) reduced population size(s), so
(much) only few alleles left;
2. Otters today from one/few surviving
population(s);
3. Inbreeding; 2 max