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Transcript
24/05/2017
Unit B1 – Influence on Life
(EdExcel)
Topic 1 - Classification
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Classification
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The world is populated by millions of different species of
animals and plants…
Classification
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How would you construct a key to classify these organisms?
Classifying organisms
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All organisms are classified into groups. For example:
Organism
What is the
main difference
between these?
Plants
Vertebrates
Amphibians
Birds
Reptiles
Animals
Invertebrates
Fish
Mammals
These 5 are called “classes” – what’s the difference between
each of these classes? How would you decide, for example, if
a whale is a mammal or a fish?
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Classifying fungi, bacteria, algae and viruses
Fungi are not classed as plants as
they have no _______ and no cell
wall, so they have their own ____.
Bacteria have no _____ and
so they are in the
“prokaryote kingdom”
Algae have features of both
plants and _____ and are
placed in the “protoctist”
kingdom.
Viruses are regarded as ____
so they have no kingdom.
Words – non-living, nuclei, chloroplasts, kingdom, animals
Classification
Organisms are classified using the following levels:
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Classification
Consider, for example, a dog:
Kingdom - Animalia
Phylum - Chordata
Class - Mammalia
Order - Carnivora
Family - Canidae
Genus - Canis
Species – C. lupus
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The 5 Kingdoms
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The 5 Kingdoms that organisms are classified by are:
Animalia
Multicellular, don’t have cell walls or chlorophyll
Plantae
Multicellular, have cell walls and chlorophyll
Fungi
Multicellular, have cell walls but no cholophyll
Protoctista
Unicellular, have a nucleus
Prokaryotes
Unicellular, have no nucleus
The Virus – Living or non-living?
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Is a virus alive?
• It contains genes
• It can reproduce
Is a virus not alive?
• It can only reproduce within a host
• It has no metabolism
Overall, scientists class them as non-living
Vertebrates
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Vertebrates are organisms with backbones and they are all
members of the phylum “chordata”, meaning “organism with a
supporting rod running the length of the body”. Some
examples:
Vertebrate or invertebrate?
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Vertebrates
Invertebrates
Differences between vertebrates
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Vertebrates have a number of significant differences.
Describe how each of the following species:
1) Absorb oxygen
2) Reproduce
3) Regulate their body temperature
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Naming Species – The Binomial System
Dog – “Canis lupus
familiaris”
Wasp – “vespula
germanica”
Human –
“homo sapien”
I invented the modern system of naming
species. I did this so that species would
have the same name in every language and so
that we would have a greater ability to study
and conserve different species.
Carolus Linnaeus, 1707-1778
Reproduction between species
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A “species” is defined as when organisms reproduce with each other to
produce fertile offspring. Different species can sometimes mate and have
offspring but they would be infertile. Some examples:
Mule
Zebroid
Liger
Geep
Similar Species
Ways in which sharks and dolphins are similar:
Ways in which sharks and dolphins are different:
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Problems with classifying species
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Ring species – these two
different types of gull
can breed with the
same other gulls but not
with each other, so are
they the same species?
Hybridisation – sometimes
different species can
interbreed and produce
fertile offspring (unlike
the geep) – so which
species is the offspring?
Adaptation
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Organisms are ADAPTED to the habitat they live in. In
other words, they have special features that help them to
survive. Some examples:
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P
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Extreme environments
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Mountains
The Arctic
Deep sea
volcanic vents
Evolution
Charles Darwin
(1809-1882)
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Evolution is the theory of slow,
continual change of organisms over
a very long time. All living things
on the Earth have supposedly
developed from the first simple
life forms that arrived
3,000,000,000 years ago.
The “Evolution Tree”
Family Hylobatidae
(Lesser Apes)
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Family Hominidae
(Great Apes)
Subfamily
Ponginae
Subfamily
Hominidae
Tribe Panini
Tribe Homini
Tribe Gorillini
Gibbons
Orangutans
Chimpanzees
Gorillas
Humans
Evolution
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The main evidence for my theory came
from fossil records. However, these
records didn’t exist when I came up
with my theory. Also, there was
little evidence about how species
evolved so few people believed my
ideas.
These days scientists understand that
the process that causes evolution is
called “Natural selection” and it
works like this:
Natural Selection
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1) Each species shows variation
and they “overpopulate” – they
produce more offspring than will
survive to adulthood:
2) There is competition within each
species for food, living space,
water, mates etc
Get off
my land
3) The “better adapted” members
of these species are more likely
to survive – “Survival of the
Fittest”
Harsh
Yum
4) These survivors will pass on their better
genes to their offspring who will also show
this beneficial variation. The “smallernecked” giraffe will eventually die out.
A smaller example
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Bacteria provide evidence for Darwin’s theory by showing the
same natural selection to become immune to antibiotics:
1) Mutation – some strains of
bacteria can develop _______
to the antibiotics.
Bacteria
No
effect!!
Penicillin
2) The non-resistant bacteria
are _____ by the _______.
3) The resistant bacteria
_______ and pass on their
mutations to their ______.
Don’t use antibiotics unless
you need to!!
Words – offspring, resistance,
killed, antibiotics, reproduce
An example – the peppered moth
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Variation
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Variation means “differences within a species. For example,
consider some of the people in your class:
Ways in which they are the same
Ways in which they are different
Would you class these variations as “continuous” or
“discontinuous”?
Environmental differences
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Some of this variation is due to our parents, but some of it is
due to our upbringing and the environment in which we live –
this is called “Environmental variation”.
Variation due to
inheritance only
Variation due to
environment only
Variation due to a
bit of both
Geographic isolation
24/05/2017
Different species can be formed by “geographic isolation”, for
example, consider an African elephant:
1) Elephants are separated by a
geographic feature e.g. a _________
2) Elephants on each side of the
mountain have different ______ in
their _____ pool
3) Their _______ die out and the
offspring are so genetically removed
that they’re incapable of ________
with each other – they’re now
different ________
Words – species, mutations, mountain, gene, ancestors, reproducing
Validating New Evidence
24/05/2017
Whenever new evidence is discovered it always has to be
validated by the scientific community, for example by:
Peer review
Publishing findings in
a scientific journal
Scientific
conferences
Genes, Chromosomes and DNA
24/05/2017
Sexual Reproduction
The human egg and
sperm cell contain 23
chromosomes each.
When fertilisation happens the
gametes fuse together to make a
single cell called a ZYGOTE. The
zygote has 46 chromosomes (23
pairs).
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Boy or Girl?
X
Y
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X
“Allele”
Girl
XX
XY
Boy
Mother
Boy or Girl?
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Son
Father
Daughter
Genotype
Phenotype
Key words
24/05/2017
•This allele determines the development of a
characteristic
•The characteristic caused by the genotype
Allele
•This allele will determine a characteristic only if
there are no dominant ones
Dominant
•This word refers to a pair of chromosomes being
made of two different alleles of a gene
Recessive
•The genetic make up in a nucleus
Homozygous
•This word refers to a pair of chromosomes being
made of two of the same alleles of a gene
•An alternative form of a gene
Heterozygous
Eye colour
24/05/2017
In eye colour the brown eye allele is dominant, so we call it
B, and the blue eye is recessive, so we call it b:
BB
Bb
bb
Homozygous
brown-eyed
parent
Heterozygous
brown-eyed
parent
Blue-eyed parent
What would the offspring have?
Eye colour
Example 1: A homozygous
brown-eyed parent and a
blue-eyed parent:
X
BB
Parents:
Gametes:
24/05/2017
Example 2: 2 heterozygous
brown-eyed parents
bb
Bb
X
Bb
B
B
b
b
B
b
B
b
Bb
Bb
Bb
Bb
BB
Bb
bB
bb
(FOIL)
Offspring:
All offspring have brown eyes
25% chance of blue eyes
Eye colour
24/05/2017
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
Bb
bb
B
b
b
b
Bb
Bb
bb
bb
Equal (50%)
chance of
being either
brown eyed or
blue eyed.
Another method –
the “Punnett Square”
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
B
b
b
Bb
bb
b
Bb
bb
Father
Mother
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Example questions
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1) In mice, white fur is dominant. What type of offspring
would you expect from a cross between a heterozygous
individual and one with grey fur? Explain your answer with a
genetic diagram.
2) A homozygous long-tailed cat is crossed with a homozygous
short-tailed cat and produces a litter of 9 long-tailed kittens.
Show the probable offspring which would be produced if two
of these kittens were mated and describe the characteristics
of the offspring (hint: work out the kitten’s genotype first).
Inherited diseases
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1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat
the lungs, gut and pancreas. It’s caused by recessive alleles:
Ff
X
Ff
2) Huntingdon's disease – a disease of the nervous system that causes
shaking and eventually dementia. It’s caused by a dominant allele:
Cc
X
cc
3) Sickle cell anaemia – a disease that alters the shape of red blood cells,
thereby reducing their oxygen capacity, causing weakness and anaemia.
It’s caused by recessive alleles:
Ss
X
Ss
Family Pedigree Charts
24/05/2017
Consider the following chart of the offspring and
grandchildren between two sickle-cell anaemia carriers:
Key:
= male
= female
= S allele
= s allele
Q. Describe the genotype and the phenotype of each
of the grandchildren. Also, which member of this
family has got sickle-cell anaemia?