30/11/14 30/11/14

Unit B1 – Influence on Life

(EdExcel)

30/11/14 Topic 1 - Classification

30/11/14 30/11/14 Classification The world is populated by millions of different species of animals and plants…

30/11/14 30/11/14 Classification How would you construct a key to classify these organisms?

30/11/14 30/11/14 Classifying organisms All organisms are classified into groups. For example:

Organism

Plants Animals

Vertebrates Invertebrates

Reptiles Fish Birds Mammals Amphibians

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?

What is the main difference between these?

30/11/14 Classifying fungi, bacteria, algae and viruses

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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

30/11/14 Classification Organisms are classified using the following levels:

Kingdom

Phylum

Class

Order

Family

Genus

Species

30/11/14 Classification Consider, for example, a dog:

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Order - Carnivora

Family - Canidae

Genus - Canis

Species – C. lupus

30/11/14 The 5 Kingdoms The 5 Kingdoms that organisms are classified by are:

Animalia

Plantae

Fungi

Protoctista

Prokaryotes

Multicellular, don’t have cell walls or chlorophyll

Multicellular, have cell walls and chlorophyll

Multicellular, have cell walls but no cholophyll

Unicellular, have a nucleus

Unicellular, have no nucleus

30/11/14 The Virus – Living or non-living?

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

30/11/14 Vertebrates 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:

30/11/14 Vertebrate or invertebrate? 30/11/14

Vertebrates Invertebrates

30/11/14 Differences between vertebrates Vertebrates have a number of significant differences.

Describe how each of the following species:

1)  Absorb oxygen

2)  Reproduce

3)  Regulate their body temperature

30/11/14 Naming Species – The Binomial System 30/11/14

Carolus Linnaeus, 1707-1778

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.

Human – “homo sapien”

Dog – “Canis lupus familiaris”

Wasp – “vespula germanica”

30/11/14 30/11/14 Reproduction between species

Liger

Geep Zebroid

Mule

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:

30/11/14 30/11/14 Similar Species

Ways in which sharks and dolphins are similar:

Ways in which sharks and dolphins are different:

30/11/14 Problems with classifying species 30/11/14

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?

30/11/14 30/11/14 Adaptation

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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30/11/14 30/11/14 Extreme environments

Deep sea volcanic vents

Mountains

The Arctic

30/11/14 30/11/14 Evolution

Charles Darwin (1809-1882)

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.

30/11/14 30/11/14 The “Evolution Tree”

Family Hominidae (Great Apes)

Family Hylobatidae (Lesser Apes)

Subfamily Hominidae

Subfamily Ponginae

Tribe Homini Tribe Panini

Tribe Gorillini

Humans Chimpanzees Gorillas Orangutans Gibbons

30/11/14 30/11/14 Evolution 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:

30/11/14 30/11/14 Natural Selection 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

4)  These survivors will pass on their better genes to their offspring who will also show this beneficial variation. The “smaller-necked” giraffe will eventually die out.

Get off my land

Harsh

Yum

3)  The “better adapted” members of these species are more likely to survive – “Survival of the Fittest”

30/11/14 30/11/14 A smaller example 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.

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!!

Bacteria

Penicillin

No effect!!

Words – offspring, resistance, killed, antibiotics, reproduce

30/11/14 30/11/14 An example – the peppered moth

30/11/14 Variation 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”?

30/11/14 Environmental differences 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

30/11/14 Geographic isolation 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

30/11/14 Validating New Evidence Whenever new evidence is discovered it always has to be validated by the scientific community, for example by:

Publishing findings in a scientific journal

Peer review

Scientific conferences

30/11/14 30/11/14 Genes, Chromosomes and DNA

30/11/14 30/11/14 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).

30/11/14 30/11/14 Boy or Girl?

X Y X

XX XY Girl Boy

“Allele”

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Father

Mother

Son

Daughter

Boy or Girl?

30/11/14 30/11/14 Key words Genotype

Phenotype

Allele

Dominant

Recessive

Homozygous

Heterozygous

• This allele determines the development of a characteristic

• The characteristic caused by the genotype

• This allele will determine a characteristic only if there are no dominant ones

• This word refers to a pair of chromosomes being made of two different alleles of a gene

• The genetic make up in a nucleus

• 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

30/11/14 30/11/14 Eye colour 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?

30/11/14 30/11/14 Eye colour Example 1: A homozygous brown-eyed parent and a

blue-eyed parent:

Example 2: 2 heterozygous brown-eyed parents

BB bb X Bb Bb X Parents:

Gametes:

Offspring: Bb Bb Bb Bb BB Bb bb bB

B B b b B b B b

(FOIL)

All offspring have brown eyes 25% chance of blue eyes

30/11/14 30/11/14 Eye colour Example 3: A heterozygous brown-eyed father and a blue-eyed mother:

Bb

Bb Bb bb bb

bb

b b B b

Equal (50%) chance of being either brown eyed or blue eyed.

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B b b b

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

30/11/14 30/11/14 Example questions 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).

30/11/14 30/11/14 Inherited diseases 1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat the lungs, gut and pancreas. It’s caused by recessive alleles:

2) Huntingdon's disease – a disease of the nervous system that causes shaking and eventually dementia. It’s caused by a dominant allele:

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:

Ff Ff X

Cc cc X

Ss Ss X

30/11/14 Family Pedigree Charts 30/11/14

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?