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Unit B1 – Influence on Unit B1 – Influence on LifeLife

(EdExcel)

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Topic 1 - Classification

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ClassificationClassificationThe world is populated by millions of different species of animals and plants…

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ClassificationClassificationHow would you construct a key to classify these organisms?

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Classifying organismsClassifying organismsAll organisms are classified into groups. For example:

Organism

Plants Animals

Vertebrates Invertebrates

Reptiles FishBirds 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?

20/04/23Classifying fungi, bacteria, algae and Classifying fungi, bacteria, algae and virusesviruses

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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

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ClassificationOrganisms are classified using the following levels:

Kingdom

Phylum

Class

Order

Family

Genus

Species

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ClassificationConsider, 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 KingdomsThe 5 Kingdoms that organisms are classified by are:

Animalia

Plantae

Fungi

Protoctista

Prokaryotes

Multicellular, don’t have cell walls or chlorophyllMulticellular, have cell walls and chlorophyll

Multicellular, have cell walls but no cholophyllUnicellular, have a nucleus

Unicellular, have no nucleus

20/04/23The 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

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VertebratesVertebrates 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:

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Vertebrate or invertebrate?Vertebrate or invertebrate?20/04/23

Vertebrates Invertebrates

20/04/23Differences 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

20/04/23Naming Species – The Binomial Naming Species – The Binomial SystemSystem

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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”

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Reproduction between speciesReproduction between species

Liger

GeepZebroid

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:

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Similar SpeciesSimilar Species

Ways in which sharks and dolphins are similar:

Ways in which sharks and dolphins are different:

20/04/23Problems with classifying Problems with classifying speciesspecies

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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?

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AdaptationAdaptation

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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PP

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Extreme environmentsExtreme environments

Deep sea volcanic

vents

Mountains

The Arctic

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EvolutionEvolution

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.

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The “Evolution Tree”The “Evolution Tree”

Family Hominidae

(Great Apes)

Family Hylobatidae (Lesser Apes)

Subfamily Hominidae

Subfamily Ponginae

Tribe HominiTribe Panini

Tribe Gorillini

HumansChimpanzees

GorillasOrangutans

Gibbons

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EvolutionEvolutionThe 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:

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Natural SelectionNatural Selection1) 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”

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A smaller exampleA smaller exampleBacteria 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

20/04/2320/04/23An example – the peppered An example – the peppered mothmoth

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VariationVariation 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”?

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Environmental differencesSome 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

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Geographic isolationDifferent 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

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Validating New EvidenceWhenever 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

20/04/2320/04/23Genes, Chromosomes and Genes, Chromosomes and DNADNA

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Sexual ReproductionSexual 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?Boy or Girl?

X Y X

XX XYGirl Boy

“Allele”

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Father

Mother

Son

Daughter

Boy or Girl?Boy or Girl?

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Key wordsKey wordsGenotype

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

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Eye colourEye 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:

bbBB Bb

Homozygous brown-eyed

parent

Heterozygous brown-eyed

parent

Blue-eyed parent

What would the offspring have?

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Eye colourEye colourExample 1: A homozygous brown-eyed parent and a

blue-eyed parent:

Example 2: 2 heterozygous brown-

eyed parents

BB bbX Bb BbXParents:

Gametes:

Offspring: Bb Bb BbBb BB Bb bbbB

B B bb B bB b

(FOIL)

All offspring have brown eyes

25% chance of blue eyes

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Eye colourEye colour

Example 3: A heterozygous brown-eyed father and a blue-eyed mother:

Bb

Bb Bb bbbb

bb

b bB b

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

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B b

b

b

Another method – Another method – the “Punnett Square”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 questionsExample 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).

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Inherited diseasesInherited diseases1) 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 FfX

Cc ccX

Ss SsX

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Family Pedigree ChartsFamily Pedigree Charts20/04/23

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?