Unit B1 - Influences on Life

Content and How Science Works overview

In Unit B1 students study three topics that enable them to find out more about how they fit into the world and how organisms are affected by and respond to internal and external influences.

Practical investigations throughout the unit will give students opportunities to plan and carry out investigations. They will devise their own models and evaluate them. They will also assess and manage risks, trial their plans and consider how the quality of their data might be improved. They will analyse data, draw conclusions providing evidence to support their conclusions, and evaluate to what degree the conclusion supports the hypothesis.

Throughout the unit, students will have the opportunity to improve and demonstrate mathematical skills. This includes learning about direct proportion and simple ratios, calculating arithmetic means, plotting and drawing graphs (line graphs, bar charts, pie charts, scatter graphs, histograms) selecting appropriate scales for the axes, translating information between graphical and numeric form, extracting and interpreting information from charts, graphs and tables, and understanding the idea of probability.

Topic 1 explores the general characteristics of animals and plants, and then looks more closely at the five vertebrate groups and organisms that can survive in extreme environments. In this topic students will learn about the problems of classifying some organisms and will study variation, as well as the basic principles of inheritance and Darwin’s theory of evolution by natural selection.

Work on classification systems shows students how data collected over time can have different interpretations and how ideas and theories change as more data is collected. The evidence we now have to support Darwin’s theory of natural selection illustrates the importance of collecting data to develop and test theories.

Work on food chains, the process of natural selection and patterns of inheritance provides opportunities to use models and theories to explain observed data.

Students will critically evaluate evidence, suggesting reasons for inconsistencies in the data collected and ways to improve precision or reproducibility of results. Students will have the opportunity to work quantitatively when collecting data and in studying percentage probabilities and biomass and energy in food chains.

In Topic 2 students will investigate how humans detect and respond to changes in their external and internal environments, including the role of hormones and the nervous system. Students will also explore the role of hormones in plants in terms of responding to stimuli.

Unit B1: Influences on life

Work on how organisms respond to change provides opportunities to see how phenomena can be explained by developing and using scientific theories, models and ideas.

Students will present information, develop arguments and draw conclusions using scientific, technical and mathematical language, conventions and symbols and ICT tools when investigating how organisms respond to change and how blood glucose levels are regulated.

Students will consider the use of contemporary science and technological developments and their benefits, drawbacks and risks when exploring the links between obesity and Type 2 diabetes, and in the commercial use of plant hormones.

Topic 3 begins by looking at the ways in which the functioning of the body is affected by external factors such as drugs and pathogens. Students will also discover how scientists have contributed to the development and use of antibiotics and antiseptics. They will go on to learn about the interdependence of organisms on Earth and natural nutrient cycles, before finding out how chemicals produced by human activities can pollute the planet on which they live.

Work on the carbon and nitrogen cycles provides opportunities to use models and theories to explain observed data.

Students will consider how decisions about, for example, smoking, drug or alcohol policies, are informed by scientific evidence of the effect on the human body. However, these decisions cannot be made using science alone as there are implications for society. We must also consider ethical issues when deciding whether to use technology; for example, when deciding whether a patient is suitable for an organ transplant.

Throughout the unit students will learn about the importance of the application of biology to improving health and food production, such as the development of new drugs and antibiotics, and the commercial uses of plant hormones. They will evaluate the advantages, disadvantages and risks of the use or misuse of drugs, and consider how decisions such as whether or not to recycle waste are taken.

Assessment overview

This unit is externally assessed, through a one hour, 60 mark, tiered written examination, containing six questions. The examination will contain a mixture of question styles, including objective questions, short answer questions and extended writing questions.

Unit B1: Influences on life

Practical investigations in this unit Within this unit, students will develop an understanding of the process of scientific investigations, including that investigations:

• use hypotheses which are tested

• require assessment and management of risks

• require the collection, presentation, analysis and interpretation of primary and secondary evidence including the use of appropriate technology

• should include a review of methodology to assess fitness for purpose

• should include a review of hypotheses in the light of outcomes.

The following specification points are practical investigations which that exemplify the scientific process and may appear in the written examination for this unit:

1.14 Investigate the variations within a species to illustrate continuous variation and discontinuous variation

2.16 Investigate tropic responses

2.22 Investigate human responses to external stimuli

3.3 Investigate reaction times

3.15 Investigate the effects of antiseptics or antibiotics on microbial cultures

3.23 Investigate the effect of pollutants on plant germination and plant growth

The following are further suggestions for practical work within this unit:

• Investigate inheritance using suitable organisms or models

• Investigate the speed of transmission of electrical impulses in the nervous system

• Investigate the presence of sugar in simulated urine/body fluids

• Investigate the effect of light and/or gravity on plant growth

• Investigate antimicrobial properties of plants

• Investigate how indicator species can be used to assess levels of pollution in water or the atmosphere

The controlled assessment task (CAT) for the GCSE in Biology will be taken from any of these practical investigations (specification points and further suggested practical work). This task will change every year, so future CATs will be chosen from this list.

Unit B1: Influences on life

Detailed unit content

In this specification bold text refers to higher tier only content. Italic text refers to practical investigations, which students are required to demonstrate an understanding of.

Topic 1

Classification, variation and inheritance

1.1 Demonstrate an understanding of how biologists classify organisms according to how closely they are related to one another including:

- Species – groups of organisms that have many features in common

- Genus – contains several species with similar characteristics

- Family – comprising of several genera

- Order – comprising of several families

- Class – comprising of several orders

- Phylum – comprising of several classes

- The Five Kingdoms – animalia, plantae, fungi, protoctista and prokaryota

1.2 Describe the main characteristics of the five kingdoms including:

- Animalia – multicellular, do not have cell walls, do not have chlorophyll, feed heterotrophically

- Plantae – multicellular, have cell walls, have chlorophyll, feed autotrophically

- Fungi – multicellular, have cell walls, do not have chlorophyll, feed saprophytically

- Protoctista – unicellular, have a nucleus

- Prokaryota – unicellular, have no nucleus

1.3 Explain why scientists do not classify viruses in any of the five kingdoms and regard them as non-living

1.4 Describe the main characteristics of the phylum Chordata as animals with a supporting rod running the length of the body, an example of this being the backbone in vertebrates

1.5 Explain how scientists place vertebrates into groups based on:

- Oxygen absorption methods – lungs, gills and skin

- Reproduction – internal or external fertilisation, oviparous or viviparous

- Thermoregulation – homeotherms and poikilotherms

1.6 Demonstrate an understanding of the problems associated with assigning vertebrates to a specific group based on their anatomy and reproduction methods and why many vertebrates are difficult to classify

Unit B1: Influences on life

1.7 Discuss why the definition of a species as organisms that produce fertile offspring may have limitations: some organisms do not always reproduce sexually and some hybrids are fertile

1.8 Explain why binomial classification is needed to identify, study and conserve species, and can be used to target conservation efforts

1.9 Explain how accurate classification may be complicated by:

- variation within a species

- hybridisation in ducks

- ring species

1.10 Construct and use keys to show how species can be identified

1.11 Explain how organisms are adapted to their environment and how some organisms have characteristics that enable them to survive in extreme environments, including deep-sea hydrothermal vents and polar regions

1.12 Demonstrate an understanding of Darwin’s theory of evolution by natural selection including:

- variation – most populations of organisms contain individuals which vary slightly from one to another

- over-production – most organisms produce more young than will survive to adulthood

- struggle for existence – because populations do not generally increase rapidly in size there must therefore be considerable competition for survival between the organisms

- survival – those with advantageous characteristics are more likely to survive this struggle

- advantageous characteristics inherited – better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring

- gradual change – over a period of time the proportion of individuals with the advantageous characteristics in the population will increase compared with the proportion of individuals with poorly adapted characteristics, and them poorly adapted characteristics may eventually be lost

1.13 Describe variation as continuous or discontinuous

1.14 Investigate the variations within a species to illustrate continuous variation and discontinuous variation

1.15 Interpret information on variation using normal distribution curves

1.16 Demonstrate an understanding of the causes of variation, including:

- genetic variation – different characteristics as a result of mutation or reproduction

- environmental variation – different characteristics caused by an organism’s environment (acquired characteristics)

Unit B1: Influences on life

1.17 Demonstrate an understanding of how speciation occurs as a result of geographic isolation

1.18 Explain how new evidence from DNA research and the emergence of resistant organisms supports Darwin’s theory

1.19 Explain the role of the scientific community in validating new evidence, including the use of:

- scientific journals

- the peer review process

- scientific conferences

1.20 Describe the structure of the nucleus of the cell as containing chromosomes, on which genes are located

1.21 Demonstrate an understanding that genes exist in alternative forms called alleles which give rise to differences in inherited characteristics

1.22 Recall the meaning of, and use appropriately, the terms: dominant, recessive, homozygous, heterozygous, phenotype and genotype

1.23 Analyse and interpret patterns of monohybrid inheritance using a genetic diagram, Punnett squares and family pedigrees

1.24 Calculate and analyse outcomes (using probabilities, ratios and percentages) from monohybrid crosses

1.25 Describe the symptoms of the genetic disorders:

- sickle cell disease

- cystic fibrosis

1.26 Evaluate the outcomes of pedigree analysis when screening for genetic disorders:

- sickle cell disease

- cystic fibrosis

Topic 2

Responses to a changing environment

2.1 Define homeostasis as the maintenance of a stable internal environment

2.2 Demonstrate an understanding of the homeostatic mechanisms of:

- thermoregulation and the effect of temperature on enzymes

- osmoregulation

- blood glucose regulation

Unit B1: Influences on life

2.3 Explain how thermoregulation takes place, with reference to the function of the skin, including:

- the role of the dermis – sweat glands, blood vessels and nerve endings, hair, erector muscles and sebaceous glands

- the role of the hypothalamus – regulating body temperature

2.4 Explain how thermoregulation takes place, with reference to:

- vasoconstriction

- vasodilation

- negative feedback

2.5 Recall that hormones are produced in endocrine glands and are transported by the blood to their target organs

2.6 Explain how blood glucose levels are regulated by insulin and excess blood glucose is converted to glycogen in the liver

2.7 Explain how blood glucose levels are regulated by causing the conversion of glycogen to glucose

2.8 Recall that Type 1 diabetes is caused by a lack of insulin

2.9 Explain how Type 1 diabetes can be controlled, including the roles of diet and injection of insulin usually into the subcutaneous fat

2.10 Explain how, in Type 1 diabetes, the level of physical activity and diet affect the amount of insulin required

2.11 Recall that Type 2 diabetes is caused by a person becoming resistant to insulin

2.12 Explain how Type 2 diabetes can be controlled by diet and physical activity

2.13 Evaluate the correlation between obesity (including calculations of BMI) and Type 2 diabetes

2.14 Explain how plant growth substances (hormones) bring about:

- positive phototropism in shoots

- positive gravitropism (geotropism) in roots

2.15 Explain how auxins bring about shoot curvature using cell elongation

2.16 Investigate tropic responses

2.17 Analyse, interpret and evaluate data from plant hormone experiments, including the action of auxins and gibberellins

Unit B1: Influences on life

2.18 Demonstrate an understanding of the uses of plant hormones, including:

- selective weedkillers

- rooting powder

- seedless fruit

- fruit ripening

2.19 Recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

2.20 Explain the structure and function of dendrons and axons in the nervous system

2.21 Describe how stimulation of receptors in the sense organs sends electrical impulses along neurones

2.22 Investigate human responses to external stimuli

2.23 Describe the structure and function of sensory, relay and motor neurones and synapses including:

- the role of the myelin sheath

- the role of neurotransmitters

- the reflex arc

Topic 3

Problems of, and solutions to a changing environment

3.1 Define a drug as a chemical substance, such as a narcotic or hallucinogen, that affects the central nervous system, causing changes in psychological behaviour and possible addiction

3.2 Describe the general effects of:

- painkillers that block nerve impulses, including morphine

- hallucinogens that distort sense perception, including LSD

- stimulants that increase the speed of reactions and neurotransmission at the synapse, including caffeine

- depressants that slow down the activity of the brain, including alcohol

3.3 Investigate reaction times

3.4 Explain the effects of some chemicals in cigarette smoke, including:

- nicotine as an addictive drug

- tar as a carcinogen

- carbon monoxide reducing the oxygen-carrying ability of the blood

3.5 Evaluate data relating to the correlation between smoking and its negative effects on health

Unit B1: Influences on life

3.6 Evaluate evidence of some harmful effects of alcohol abuse:

- in the short term – blurred vision, lowering of inhibitions, slowing of reactions

- in the long term – liver cirrhosis, brain damage

3.7 Discuss the ethics of organ transplants, including:

- liver transplants for alcoholics

- heart transplants for the clinically obese

- the supply of organs

3.8 Recall that infectious diseases are caused by pathogens

3.9 Describe how pathogens are spread, including:

- in water, including cholera bacterium

- by food, including Salmonella bacterium

- airborne (eg sneezing), including influenza virus

- by contact, including athlete’s foot fungus

- by body fluids, including HIV

- by animal vectors, including:

 i housefly: dysentery bacterium

ii Anopheles mosquito: malarial protozoan

3.10 Explain how the human body can be effective against attack from pathogens, including:

- physical barriers – skin, cilia, mucus

- chemical defence – hydrochloric acid in the stomach, lysozymes in tears

3.11 Demonstrate an understanding that plants produce chemicals that have antibacterial effects in order to defend themselves, some of which are used by humans

3.12 Describe how antiseptics can be used to prevent the spread of infection

3.13 Explain the use of antibiotics to control infection, including:

- antibacterials to treat bacterial infections

- antifungals to treat fungal infections

3.14 Evaluate evidence that resistant strains of bacteria, including MRSA, can arise from the misuse of antibiotics

3.15 Investigate the effects of antiseptics or antibiotics on microbial cultures

3.16 Recall that interdependence is the dynamic relationship between all living things

3.17 Demonstrate an understanding of how some energy is transferred to less useful forms at each trophic level and this limits the length of a food chain

Unit B1: Influences on life

3.18 Demonstrate an understanding that the shape of a pyramid of biomass is determined by energy transferred at each trophic level

3.19 Explain how the survival of some organisms may depend on the presence of another species:

- parasitism, including:

i fleas

ii head lice

iii tapeworms

iv mistletoe

- mutualism, including:

i oxpeckers that clean other species

ii cleaner fish

iii nitrogen-fixing bacteria in legumes

iv chemosynthetic bacteria in tube worms in deep-sea vents

3.20 Analyse, interpret and evaluate data on global population change

3.21 Explain how the increase in human population contributes to an increase in the production of pollutants, including phosphates, nitrates and sulfur dioxide (acid rain)

3.22 Explain how eutrophication occurs and the problems associated with eutrophication in an aquatic environment

3.23 Investigate the effect of pollutants on plant germination and plant growth

3.24 Demonstrate an understanding of how scientists can use the presence or absence of indicator species as evidence to assess the level of pollution:

- polluted water indicator – bloodworm, sludgeworm

- clean water indicator – stonefly, freshwater shrimps

- air quality indicator – lichen species, blackspot fungus on roses

3.25 Demonstrate an understanding of how recycling can reduce the demand for resources and the problem of waste disposal, including paper, plastics and metals

3.26 Demonstrate an understanding of how carbon is recycled:

- during photosynthesis plants remove carbon dioxide from the atmosphere

- carbon compounds pass along a food chain

- during respiration organisms release carbon dioxide into the atmosphere

- decomposers release carbon dioxide into the atmosphere

- combustion of fossil fuels releases carbon dioxide into the atmosphere

Unit B1: Influences on life

3.27 Demonstrate an understanding of how nitrogen is recycled:

-plants and animals

- nitrogen-fixing bacteria living in root nodules or the soil can fix nitrogen gas

- the action of lightning can convert nitrogen gas into nitrates

- decomposers break down dead animals and plants

- soil bacteria convert proteins and urea into ammonia

- nitrifying bacteria convert this ammonia to nitrates

- plants absorb nitrates from the soil

- nitrates are needed by plants to make proteins for growth

- nitrogen compounds pass along a food chain or web

- denitrifying bacteria convert nitrates to nitrogen gas