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Science B1 Topic 1
GCSE edexcel core science biology: classification, variation, inheritance
| Question | Answer |
|---|---|
| How do scientists classify organisms? | Species, genus, family, order, class, phylum, kingdom |
| What is classification? | The process of sorting organisms into groups according to their characteristics. |
| What are the main characteristics of the kingdom: animalia? | Multicelluar; feed heterotrophically; no cell walls; no chlorophyll; complex cell structure with nucleus |
| What are the main characteristics of the kingdom: plantae? | Multicelluar; feed autotrphically; cell walls made out of cellulose; have chlorophyll; complex cell structure with nucleus |
| What are the main characteristics of the kingdom: fungi? | Multicellular; feed saprophytically; cell walls not made out of cellulose; no chlorophyll; complex cell structure with nucleus |
| What are the main characteristics of the kingdom: protoctista? | Unicellular; complex cell structure with nucleus |
| What are the main characteristics of the kingdom: prokaryotes? | Unicellular; simple cell structure without a nulceus; cell wall |
| What is autotrophic feeding? | Where organisms make their own food from small molecules using an energy source (e.g. light) |
| What is heterotrophic feeding? | Where organisms get food by eating and digesting the tissues of other organisms |
| What is saprophytic feeding? | Where organisms get food by digesting the tissues of other organisms outside the body then absorbing the digested food |
| Why are viruses not in one of the kingdoms? | Although they can change the way a cell works so that it makes copies of the virus, they don't show signs of other life processes e.g. growth and feeding |
| What is the main feature of animals in the phylum chordata? | A supporting rod running the length of the body (e.g. a backbone in vertebrates) |
| What is the difference between vertebrates and invertebrates? | Vertebrates have backbones (made up of vertebrae) but invertebrates don't have a backbone |
| What are the ways that scientists group vertebrates? | 1) Oxygen absorption methods: lungs, gills or moist skin 2) reproduction: internal or external fertilisation, vivparous or oviparous 3) thermoregulation: poikilotherms or homeotherms |
| What is the difference between poikilotherms and homeotherms? | Poikilotherms- body temperature varies with temperature of the surroundings Homeotherms- body temperature stays more constant and warm than surroundings |
| Which animals are oviparous/ vivparous? | Oviparous animals lay eggs e.g. birds, reptiles. Viviparous animals give birth to live young e.g. mammals |
| Why is it difficult to assign vertebrates to a specific group? (examples)How is this problem overcome? | Some animals in a species have different characteristics e.g.some adult amphibians have lungs, and shark are fish but use internal fertilisation and give birth to live young. Scientists look at many characteristics to classify organisms to solve this |
| What is a species? | A species is a group of organisms what can interbreed to produce fertile offspring. |
| What are some problems with the definition of a species? | 1) some hybrids are fertile 2) some organisms don't need to interbreed to reproduce- so we don't know if individuals are in the same species e.g. plants and fungi: new plant grows from adult plant, bacteria and protoctists split in half |
| What are some difficulties with classification? | 1) mallard ducks can hybridise to produce fertile hybrids- which creates ducks with a continuous range of characteristics 2) ring species can occur and there is a gradual range of characteristics 3) variation within a species |
| How can scientists test that a 'new' organism isn't just a hybrid or a result of variation? | They find more than one of that organism |
| What are the ways that the scientific community validates new evidence? | 1)scientists publish their ideas in scientific journals for others to validate 2)scientists use the peer review process- they share their work with another scientist who says whether the evidence should be published 3)they attend scientific conferences |
| What is the binomial classification system? | A way of classifying organisms so that their name is their genus then their species |
| What are the advantages of accurate classification using the binomial system? | * you can tell from the name if organisms are related * scientists all over the world can communicate * organisms with the same common names may be different species * easily identify new and existing species *identify areas of greater/lesser biodiver |
| What is biodiversity? | The measure of the total number of different species in an area |
| Why is classification important when measuring biodiversity? | As you need to know whether organisms belong to the same or different species to get an accurate measurement |
| What are biodiversity hotspots? | Areas of greater biodiversity e.g. amazon rainforest in south america |
| Where to scientists want to conserve? | Scientists want to spend money on conserving areas of greater biodiversity because they contain more species that we rely on for food and medicine. |
| Which areas recover from natural disasters the best? | Areas of greater biodiversity |
| What is adaptation? | Adaptation where organisms evolve characteristics that allow them to survive in their habitat |
| How is the polar bear adapted to its environment? | * rough soles on feet to grip ice * white fur for camouflage * large feet are good for swimming and spread out weight * small ears to stop it losing to much heat * thick fur and blubber for insulation |
| What are deep-sea hydrothermal vents and what are the conditions around them? | They are large vents where hot fluids come out and solidify very quickly. There is complete darkness, large temperature changes, and high pressures. |
| How is a deep-sea pompeii worm adapted to its environment? | * sensitive tentacles instead of eyes * spends time in a papery tube to protect it from predators * body can cope with very high pressures * layer of bacteria covering body protects it from the heat |
| What is inherited variation? | Variation that is a result of your genes- caused by reproduction and nuclei fusing to produce a different gene mix every time. Also caused by cell mutations. e.g. genetic diseases, blood group, natural hair and eye colours |
| What is environmental variation? | Variation that is a result of an organisms environment- they are acquired characteristics. e.g. accent Most characteristics are partially inherited and acquired. |
| What is discontinuous variation? | Variation where there is a fixed set of possible values e.g. shoe size, blood group |
| What is continuous variation? | Variation where values can be any number within a range e.g height, weight |
| What is a normal distribution curve? | Continuous variation can be plotted on a graph and it often shows a normal distribution curve- where most individuals measure in the middle of the range and fewer measure at the extremes. The curve looks bell shaped. |
| What is qualitative data? | Data that is in the form of descriptions e.g. blood group: 0 people |
| What is quantitative data? | Data that is measured in numerical values e.g height: 150cm |
| What is evolution? | Gradual change over time due to competition, survival of the fittest, and the passing down of beneficial genes |
| What is Darwin's theory of evolution by natural selection? | Overproduction of offspring causes struggle for existence and competition. Offspring show variation and some are better adapted to the environment. Natural selection/ survival of the fittest occurs. Surviving organisms pass on advantageous genes. |
| When would Darwin's theory of evolution by natural selection occur? | When the environment changes gradually. |
| When would extinction occur? | When the environment changes very rapidly and no individuals have adaptations that allow them to survive. |
| What was some observable evidence for Darwin's theory? | Emergence of resistant organisms: warfarin used to poison rats. The resistant rats bred and passes on their characteristic, changing most of the population. MRSA bacteria are another example. |
| What is speciation? | A process where organisms from one species are separated by a physical barrier where the conditions are different. The individuals adapt to their environments. The individuals adapt so much overtime that the two groups can't interbreed. |
| Where did Darwin see an example of speciation? | Mockingbirds on different Galapagos Isalnds. |
| What are most animal cells made up of? | Cytoplasm, nucleus, cell membrane. |
| What is found inside the nucleus? | Long strands of DNA that form structures called chromosomes- there are two copies of each chromosome. |
| What are genes? | Genes are short sections of DNA found on chromosomes that code for a specific protein. |
| What are alleles? | Alleles are different forms of the same gene e.g. blue/brown eyes |
| Why does everyone look different? | As we all have different gene and allele combinations. |
| What are gametes? | Sex cells, produced by animals and plants. |
| What are the male gametes? | PLANTS: pollen grains ANIMALS: sperm cells |
| What are the female gametes? | PLANTS: egg cells ANIMALS: egg cells |
| How many copies of each chromosome do gametes have and why? | They only have one set, so when they fuse together in sexual reproduction, they create offspring with both sets. |
| What is a dominant allele? | The allele that will always have an effect- its characteristic will always be expressed. |
| What is a recessive allele? | The allele that will only have an effect if both of the alleles are recessive. |
| How do you write dominant and recessive alleles? | Dominant: capital letters Recessive: lowercase letters |
| What is a genotype? | The alleles in the organism e.g. Rr |
| What is a phenotype? | The description of the characteristics that the alleles cause e.g. blue eyes |
| What alleles does (a) a homozygous dominant person have, and (b) a homozygous recessive person have? | (a)2 dominant alleles, (b) 2 recessive alleles |
| What alleles does a heterozygous individual have? | One dominant and one recessive allele. |
| Two parents who are heterozygous for cystic fibrosis have a child. What chance does it have of (a) suffering from cystic fibrosis, (b) being a carrier of cystic fibrosis? | (a) 25%, (b) 50%. |
| What is sickle cell disease? | A genetic disorder caused by a faulty allele that is recessive. |
| What are the symptoms of sickle cell disease? | Tiredness, short of breath, red blood cells stick together blocking blood vessels, painful joints. |
| What is cystic fibrosis? | A genetic disorder caused by a faulty allele that is recessive. |
| What are the symptoms of cystic fibrosis? | Mucus clogs lungs, breathing is difficult, infections, tubes leading enzymes to small intestine are blocked by mucus-lack of enzymes to digest food causes weight loss. |
| What does a family pedigree chart show? | How a genetic disorder is passed through a family. |
| What is pedigree analysis? | Analysis of a family to work out the probability that a person has an inherited disease. If risks are high, people have tests for the faulty allele. |
| What is genetic screening? | A process that is done for couples who are worried about passing a genetic disorder to their children- it helps them to chose whether to have children or not. |
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