human interactions in an ecosystem and explain their impact on biodiversity.
Scientists and concerned citizens have put in place programmes to reduce the negative effects of humans on ecosystems and biodiversity.
These include:
• breeding programmes for endangered species • protection and regeneration of rare habitats
• reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop
• reduction of deforestation and carbon dioxide emissions by some governments
• recycling resources rather than dumping waste in landfill.
WS 1.4, 1.5
Evaluate given information about methods that can be used to tackle problems caused by human impacts on the environment.
Explain and evaluate the conflicting pressures on maintaining biodiversity given appropriate information.
4.8 Key ideas
The complex and diverse phenomena of the natural world can be described in terms of a small number of key ideas in biology.
These key ideas are of universal application, and we have embedded them throughout the subject content. They underpin many aspects of the science assessment.
Key ideas in biology:
• life processes depend on molecules whose structure is related to their function
• the fundamental units of living organisms are cells, which may be part of highly adapted structures including tissues, organs and organ systems, enabling living processes to be performed effectively • living organisms may form populations of single species, communities of many species and
ecosystems, interacting with each other, with the environment and with humans in many different ways
• living organisms are interdependent and show adaptations to their environment
• life on Earth is dependent on photosynthesis in which green plants and algae trap light from the Sun to fix carbon dioxide and combine it with hydrogen from water to make organic compounds and oxygen
• organic compounds are used as fuels in cellular respiration to allow the other chemical reactions necessary for life
• the chemicals in ecosystems are continually cycling through the natural world
• the characteristics of a living organism are influenced by its genome and its interaction with the environment
• evolution occurs by a process of natural selection and accounts both for biodiversity and how organisms are all related to varying degrees.
5 Chemistry subject content
This specification is presented in a two column format.The subject content is split into three sections for each of the subject areas: biology, chemistry and physics.
The left hand column contains the subject content that all students must cover, and that can be assessed in the written papers.
The right hand column exemplifies some of the key opportunities for the following skills to be developed throughout the course: WS refers to Working scientifically, MS refers to Mathematical requirements and AT refers to Use of apparatus and techniques. These are not the only opportunities. Teachers are encouraged to introduce all of these skills where appropriate throughout the course.
Each topic begins with an overview. The overview puts the topic into a broader context and is intended to encourage an overarching approach to both the teaching and learning of each of the topic areas. It is not directly assessed. Any assessable content in this overview is replicated in the left hand column. Content that is only applicable to Higher Tier is indicated by (HT only) either next to the topic heading where it applies to the whole topic or immediately preceding each paragraph or bullet point as
applicable.
It is good practice to teach and develop all of the mathematical skills throughout the course. Some mathematical skills will only be assessed in certain subject areas. These are detailed in Mathematical requirements.
Science is a practical subject. Details of the assessment of required practicals can be found in Required practical activities.
Working scientifically and Use of apparatus and techniques skills will be assessed across all papers. In chemistry paper 2 students will be expected to know and understand some basic
concepts and principles from topics in paper 1: Atomic structure and the periodic table, Bonding, structure, and the properties of matter and Quantitative chemistry.
They should be able to recall and use this knowledge in questions that link and use these principles as elements of explanations, in either paper. Students should expect to see questions based on some of these basic principles in the second paper.
5.1 Atomic structure and the periodic table
The periodic table provides chemists with a structured organisation of the known chemical elements from which they can make sense of their physical and chemical properties. The historical development of the periodic table and models of atomic structure provide good examples of how scientific ideas and explanations develop over time as new evidence emerges. The arrangement of elements in the modern periodic table can be explained in terms of atomic structure which provides evidence for the model of a nuclear atom with electrons in energy levels.