Unit B1 Influence on Life (EdExcel)
Topic 1 - Classification
Classification The world is populated by millions of different species of animals and plants
Classification How would you construct a key to classify these organisms?
Classifying organisms All organisms are classified into groups. For example: What is the main difference between these? Plants Organism Animals Vertebrates Invertebrates Amphibians Birds Reptiles 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?
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
Classification Consider, for example, a dog: Kingdom - Animalia Phylum - Chordata Class - Mammalia Order - Carnivora Family - Canidae Genus - Canis Species C. lupus
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
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
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:
Vertebrate or invertebrate? Vertebrates Invertebrates
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
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
Zebroid Geep Reproduction between species 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 Liger
Similar Species Ways in which sharks and dolphins are similar: Ways in which sharks and dolphins are different:
Problems with classifying species 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 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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Extreme environments Mountains The Arctic Deep sea volcanic vents
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.
The Evolution Tree Family Hylobatidae (Lesser Apes) Subfamily Ponginae Family Hominidae (Great Apes) Subfamily Hominidae Tribe Panini Tribe Homini Tribe Gorillini Gibbons Orangutans Chimpanzees Gorillas Humans
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:
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. Natural Selection 1) Each species shows variation and they overpopulate they produce more offspring than will survive to adulthood: Get off my land 2) There is competition within each species for food, living space, water, mates etc 3) The better adapted members of these species are more likely to survive Survival of the Fittest Harsh Yum
A smaller example Bacteria provide evidence for Darwin s theory by showing the same natural selection to become immune to antibiotics: Bacteria 1) Mutation some strains of bacteria can develop to the antibiotics. No effect!! 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!! Penicillin Words offspring, resistance, killed, antibiotics, reproduce
An example the peppered moth
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?
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
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
Validating New Evidence 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
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).
Boy or Girl? X Y X Allele Girl XX XY Boy
Mother Boy or Girl? Son Father Daughter
Key words Genotype Phenotype Allele Dominant Recessive Homozygous 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 Heterozygous
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?
Eye colour Example 1: A homozygous brown-eyed parent and a blue-eyed parent: Example 2: 2 heterozygous brown-eyed parents Parents: BB X bb Bb X Bb Gametes: B B b b B b B b (FOIL) Offspring: Bb Bb Bb Bb BB Bb bb bb All offspring have brown eyes 25% chance of blue eyes
Eye colour Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Bb bb B b b b Equal (50%) chance of being either brown eyed or blue eyed. Bb Bb bb bb
Another method the Punnett Square Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Mother Father B b b Bb bb b Bb bb
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).
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: 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 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?