24/05/2017 Unit B1 – Influence on Life (EdExcel) Topic 1 - Classification 24/05/2017 Classification 24/05/2017 The world is populated by millions of different species of animals and plants… Classification 24/05/2017 How would you construct a key to classify these organisms? Classifying organisms 24/05/2017 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? 24/05/2017 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 24/05/2017 Classification Consider, for example, a dog: Kingdom - Animalia Phylum - Chordata Class - Mammalia Order - Carnivora Family - Canidae Genus - Canis Species – C. lupus 24/05/2017 The 5 Kingdoms 24/05/2017 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? 24/05/2017 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 24/05/2017 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? 24/05/2017 Vertebrates Invertebrates Differences between vertebrates 24/05/2017 Vertebrates have a number of significant differences. Describe how each of the following species: 1) Absorb oxygen 2) Reproduce 3) Regulate their body temperature 24/05/2017 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 24/05/2017 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: 24/05/2017 Problems with classifying species 24/05/2017 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 24/05/2017 Organisms are ADAPTED to the habitat they live in. In other words, they have special features that help them to survive. Some examples: 24/05/2017 24/05/2017 P 24/05/2017 24/05/2017 Extreme environments 24/05/2017 Mountains The Arctic Deep sea volcanic vents Evolution Charles Darwin (1809-1882) 24/05/2017 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) 24/05/2017 Family Hominidae (Great Apes) Subfamily Ponginae Subfamily Hominidae Tribe Panini Tribe Homini Tribe Gorillini Gibbons Orangutans Chimpanzees Gorillas Humans Evolution 24/05/2017 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 24/05/2017 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 24/05/2017 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 24/05/2017 Variation 24/05/2017 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 24/05/2017 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). 24/05/2017 Boy or Girl? X Y 24/05/2017 X “Allele” Girl XX XY Boy Mother Boy or Girl? 24/05/2017 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 24/05/2017 Example questions 24/05/2017 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 24/05/2017 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?