Topic 5.3: Populations

5.3.1 Outline how population size is affected by natality, immigration, mortality and emigration

5.3.2 Draw and label a graph showing a sigmoid (S-shaped) population growth curve

5.3.3 Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases

5.3.4 List three factors that set limits to population increase

Topic 5.2: The greenhouse effect

5.2.1 Draw and label a diagram of the carbon cycle to show the processes involved

5.2.2 Analyse the changes in concentration of atmospheric carbon dioxide using historical records

5.2.3 Explain the relationship between rises in concentration of atmospheric carbon dioxide, methane and oxides of nitrogen and enhanced greenhouse effect.

5.2.4 Outline the precautionary principle

5.2.5 Evaluate the precautionary principle as a justification for strong action in response to the threats posed by enhanced greenhouse effect

5.2.6 Outline the consequences of a global temperature rise on arctic ecosystems

Topic 5.1: Communities and ecosystems

5.1.1 Define species, habitat, population, community, ecosystem and ecology

Species is a group of organisms that can interbreed and produce fertile, viable offspring

Habitat is an environment in which a species normally lives or the location of a living organism

Population is a group of organism of the same species who live in the same area at the same time

Community is a group of populations living and interacting with each other in an area

Ecosystem is a community and its abiotic environment

Ecology is the study of relationships between living organisms and between organisms and their environment.

5.1.2 Distinguish between autotroph and heterotroph

Autotroph is an organism that synthesizes its organic molecules from simple inorganic substances such as carbon dioxide and nitrates. Autotroph are producers.

Heterotroph is an organism that obtains organic molecules from other organisms. Heterotroph are consumers.

5.1.3 Distinguish between consumers, detritivores and saprotrophs

Consumers is an organism that ingests other organic matter that is living or recently killed

Detritivore is an organism that ingest non-living organic matter

Saprotroph is an organism that lives on or in non-living organic matter, secreting digestive enzymes into and absorbing products of digestion

5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms)

A food chain shows the linear feeding relationship between species in a community. An arrow is commonly used to represent the transfer of energy. Thus the arrow is pointing towards the consumer.

5.1.5 Describe what is meant by a food web

A food web is a diagram that shows multiple food chains together. It shows a more complete and complex feeding relationships within a community.

5.1.6 Define trophic level

An organisms trophic level refers to the position they are in on the food chain. Refer to the diagram below.

5.1.7 Deduce the trophic level of organisms in a food chain and a food web

An organism can have multiple trophic level. Find the trophic levels by counting how many past

5.1.8 Construct a food web containing up to 10 organisms, using appropriate information



5.1.9 State that light is the initial energy source for almost all communities



5.1.10 Explain the energy flow in a food chain



5.1.11 State that energy transformations are never 100% efficient



5.1.12 Explain reasons for the shape of pyramids of energy



5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled



5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients

Topic 5: Ecology and evolution

Topic 5 of the IB SL Biology syllabus is the Ecology and evolution. IBO recommends to spend 16 hours on this topic.

This topic has 5 sub-chapters: "Communities and ecosystems", "The greenhouse effect", "Populations", "Evolution", and "Classification". Each are separated with numerical values in order of mentioned.

These are all SL syllabus statements, it is recommended to bring a Casio Graphical Calculator instead of Texas.

Option H6: Gas exchange

H.6.1 Define partial pressure

H.6.2 Explain the oxygen dissociation curves of adult haemoglobin, fetal haemoglobin and myoglobin

H.6.3 Describe how carbon dioxide is carried by the blood, including the action of carbonic anhydrase, the chloride shift and buffering by plasma proteins

H.6.4 Explain the role of the Bohr shift in the supply of oxygen to respiring tissues

H.6.5 Explain how and why ventilation rate varies with exercise

H.6.6 Outline the possible causes of asthma and its effects on the gas exchange system

H.6.7 Explain the problem of gas exchange at high altitudes and the way the body acclimatizes

Option H5: The transport system

H.5.1 Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole and heart sounds

H.5.2 Analyse data showing pressure and volume changes in the left atrium, left ventricle and the aorta, during cardiac cycle.

H.5.3 Outline the mechanisms that control the heartbeat, including the roles of the SA (sinoatrial) node, AV (atrioventricular) node and conducting fibres in the ventricular walls

H.5.4 Outline atherosclerosis and the causes of cononary thrombosis

H.5.5 Discuss factors that affect the incidence of cononary heart disease

Option H4: Functions of the liver

H.4.1 Outline the circulation of the blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein

H.4.2 Explain the role of the liver in regulating levels of nutrients in the blood

H.4.3 Outline the role of the liver in the storage of nutrients, including carbohydrates, iron, vitamin A and vitamin D

H.4.4 State that the liver synthesizes plasma protein and cholesterol

H.4.5 State that the liver has a role in detoxification

H.4.6 Describe the process of erythrocyte and haemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment formation

H.4.7 Explain the liver damage caused by excessive alcohol consumption