MYP 5 Individuals & Societies (Term 1)

MYP Year 5 · Individuals & Societies · Term 1 — complete revision notes on biomes, population change and sustainable cities, then human rights, the UDHR and the great movements of social protest.

Unit 1 · Biomes & the Physical Environment

This unit builds a working model of how the living skin of the planet is organised. It answers three linked questions that run through the whole of physical and environmental geography: what the great living zones of Earth are, why they sit where they do, and how the flows of energy, water and nutrients inside them keep them alive. From that foundation we can then reason clearly about the pressures that human activity places on these systems and about the choices — protection, restoration, sustainable use — that societies make in response. The unit is deliberately built like a chain of causation: sunlight and the shape of the Earth drive climate; climate and soil select vegetation; vegetation supports animals and shapes whole communities; and those communities deliver the ecosystem services that human wellbeing quietly depends on. Break one link and you can predict the consequences down the chain — which is exactly the kind of reasoning MYP Individuals & Societies asks you to demonstrate.

1 · Unit overview & MYP framing

Before the content, it is worth being explicit about the conceptual scaffolding, because the MYP rewards you for thinking conceptually — for seeing a rainforest not as a list of plants but as a system of interactions, and for transferring an idea learned in one biome to a completely different one. The framing below is a worked example of how a teacher might set up this unit; your own school's planner may phrase it differently, and that is fine.

MYP conceptual framing (sample)

• Key concept — Global interactions / Systems. Biomes are open systems: they exchange energy and matter with the atmosphere, the oceans and, increasingly, with human economies on the other side of the world. A choice made by a consumer in one continent (for beef, palm oil, timber, soy) reaches into a biome on another. That web of exchange is the "global interaction" at the heart of the unit.

• Related concepts — sustainability, management, resources, causality. These are the recurring lenses. Resources asks what a biome provides; management asks how humans steer their use of it; sustainability asks whether that use can continue without degrading the system; and causality forces us to trace chains of cause and effect rather than settle for a single "reason".

• Global context — Globalization and sustainability (fairness and development; environment). The context orients the whole inquiry towards the tension between global economic development and the long-term health of the environment that underwrites it.

Sample statement of inquiry: "The way human systems interact with natural systems determines whether the resources a biome provides can be sustained for future generations."

Inquiry questions. Factual: Where are the world's major biomes and what characterises each? Conceptual: How does climate cause the global pattern of biomes, and how do organisms adapt to their conditions? Debatable: Should the needs of local communities or the interests of the global environment take priority when a biome is threatened?

Keep these lenses beside you as you read. When you reach the Amazon case study, for instance, you should be able to name the resources at stake, the interactions driving change, the management options on the table, and the sustainability trade-off between them — that is the difference between describing a biome and analysing it.

2 · What is a biome?

Three words are used loosely in everyday speech but must be kept sharply distinct in geography: climate , ecosystem and biome . Confusing them is the single most common error in this unit, so we define each carefully and by scale.

Climate — the long-run state of the atmosphere

Climate is the average pattern of weather at a place taken over a long period, conventionally thirty years or more. It is described mainly by two variables — temperature and precipitation — together with their seasonal distribution: not just how much rain falls, but when , and not just the mean temperature, but the annual range. Climate is a purely physical, atmospheric idea; it contains no living things. It is, however, the master control: because plants are rooted and cannot move to follow better conditions, the climate of a place effectively sets the menu of vegetation that can survive there.

Ecosystem — a community plus its physical environment

An ecosystem is a community of living organisms (the biotic component — plants, animals, fungi, microbes) interacting with the non-living physical environment (the abiotic component — climate, soil, water, sunlight, air) as a functioning unit through which energy flows and nutrients cycle. Crucially, an ecosystem has no fixed size . A single fallen log with its beetles, fungi and woodlice is an ecosystem; so is a rock pool, a hedgerow, a pond, a whole forest, or — at the largest scale — the entire biosphere. The defining feature is not scale but function: an ecosystem is any unit within which the biotic and abiotic parts are linked by the flow of energy and the cycling of matter.

Biome — a global-scale community type defined by climate

A biome is the largest recognised category of ecosystem: a very large-scale community of plants and animals, occurring across whole continents, that is characterised by a distinctive dominant vegetation type and shaped principally by climate . Tropical rainforest is a biome; so is hot desert, tundra, savanna, taiga. A biome is defined by its climate-driven vegetation structure rather than by the exact species present. This is why the concept is so powerful: the rainforests of the Amazon, the Congo and Southeast Asia share almost no species, yet all three are "tropical rainforest" because the same hot, wet climate produces the same tall, layered, evergreen, broadleaved forest structure. Biome is a functional and structural category, not a species list.

"A biome is a major regional group of distinctive plant and animal communities best adapted to the region's physical natural environment, latitude, altitude and terrain." — a standard textbook definition, useful because it foregrounds adaptation and physical environment as the organising ideas.

The relationship between the three is nested and hierarchical. Climate (abiotic, atmospheric) selects the vegetation. Vegetation plus its animals plus the physical setting form an ecosystem, which can be any size. When ecosystems of the same broad structure recur across the globe under the same climate, we group them as a biome. In short: climate → ecosystem → biome is a ladder of increasing scale and integration. A worked example: "Mediterranean climate" (hot dry summers, mild wet winters) is the climate; a particular Californian chaparral hillside with its shrubs, lizards and soil is an ecosystem; "Mediterranean / chaparral" as it recurs in California, central Chile, the Cape of South Africa, southwest Australia and around the Mediterranean Sea itself is the biome.

3 · Why biomes sit where they do

The global distribution of biomes is not random — it is startlingly orderly, arranged in broad latitudinal belts that repeat, roughly mirror-imaged, north and south of the Equator. That order exists because the two variables that define climate, temperature and precipitation, are themselves distributed in a predictable pattern controlled by the shape of the Earth and its atmospheric circulation. This section is the physical-geography engine of the whole unit; understand it and the map of biomes stops being a thing to memorise and becomes a thing you can derive .

Latitude and the global temperature gradient

Because the Earth is a sphere, the Sun's rays strike the surface at different angles at different latitudes. Near the Equator the Sun is high overhead and its energy is concentrated on a small area; near the poles the same beam of energy strikes at a low, glancing angle and is spread over a much larger area (and passes through more atmosphere, losing more to reflection and absorption). The result is the fundamental fact of world climate: it is hot at the Equator and cold at the poles , with a broadly continuous gradient between. Temperature therefore falls, on average, as you move away from the Equator. The axial tilt of 23.5° adds the seasons: as the Earth orbits, first one hemisphere then the other leans toward the Sun, so the zone of most direct heating migrates north and south through the year, which is why the tropics are hot all year while high latitudes swing between warm summers and cold winters.

Pressure belts and the global precipitation pattern

Precipitation is governed by the great convection cells of the atmosphere, which arise directly from that unequal heating. Intense heating at the Equator makes air rise; rising air cools, its water vapour condenses, and it rains heavily — this is the low-pressure belt of the Intertropical Convergence Zone, and it is why the wettest biomes on Earth (tropical rainforests) straddle the Equator. That risen air spreads polewards high in the atmosphere, cools further, and descends at around 30° north and south. Descending air warms and dries as it sinks, suppressing cloud and rain — this is the subtropical high-pressure belt , and it is why the great hot deserts of the world (Sahara, Arabian, Kalahari, Australian, Atacama-fringe) form in a ring at roughly 30° latitude. The circulation loop between the equatorial low and the subtropical high is the Hadley cell . Poleward of that, near 60°, warm air from the mid-latitudes meets cold polar air and is forced up again along the polar front, giving a second low-pressure, wetter belt (temperate forests and grasslands). Finally, cold dense air sinking over the poles gives high pressure and very low precipitation — the polar deserts and tundra.

The pattern in one line

Rising air = low pressure = wet (Equator ~0°, and ~60°); sinking air = high pressure = dry (subtropics ~30°, and the poles ~90°). Overlay this precipitation pattern on the Equator-to-pole temperature gradient and the world's biomes fall out almost automatically: hot+wet rainforest at the Equator, hot+dry desert near 30°, and progressively cooler forests, grasslands, taiga and tundra as you march toward the poles.

Two further controls fine-tune this zonal pattern and explain the exceptions. Continentality — distance from the moderating influence of the sea — makes continental interiors hotter in summer, colder in winter and drier overall, which is why the great temperate grasslands (Prairies, Steppe, Pampas) sit deep inside continents. Altitude lowers temperature by roughly 6.5 °C per 1000 m of ascent, so a tall tropical mountain can stack rainforest, temperate forest, alpine grassland and even permanent snow one above the other — a vertical compression of the whole latitudinal sequence. Ocean currents (warm currents such as the North Atlantic Drift warming western Europe; cold currents such as the Humboldt chilling and drying coastal Peru and Chile) and rain shadows behind mountain ranges account for most of the remaining local anomalies.

4 · The world's major biomes — a comparative survey

We now work through the terrestrial biomes one by one. The comparison table gives the skeleton; the paragraphs that follow put flesh on it, with particular attention — as the syllabus demands — to the adaptations by which plants and animals survive each set of conditions. Read the table across the rows to see how climate drives soils, which drive vegetation, which shapes animal life; read it down the columns to compare like with like.

Tropical grassland / savanna

Poleward of the rainforest, where the wet equatorial belt gives way to a climate with a pronounced dry season , the forest thins into savanna: a sea of tall grasses dotted with scattered trees. The defining feature is seasonality — a hot wet season of vigorous grass growth followed by a hot dry season when the grass browns off and fire is common. Vegetation is adapted to survive both drought and fire. Trees such as the acacia are often flat-topped, with tiny leaves and thorns to cut water loss and deter browsers; the baobab stores water in a hugely swollen trunk to ride out the dry months. Grasses grow from the base, so they regrow quickly after grazing or burning, and many trees have thick, fire-resistant bark. The savanna supports the world's most celebrated assemblages of large mammals — the great grazing herds of wildebeest, zebra and antelope and the predators that follow them — many of which migrate to track the rains and the flush of new grass. Fire is not merely a hazard here but an ecological force that keeps the grassland open by killing tree seedlings; suppress fire and woodland encroaches.

Hot desert

Under the descending, drying air of the subtropical high-pressure belt near 30°, precipitation collapses and the hot deserts form. Rain is scarce (under 250 mm), erratic and often evaporates before reaching the ground; cloudless skies make days scorching and, without insulating cloud, nights surprisingly cold. Life here is dominated by the single problem of water. Plants are xerophytes — built to conserve every drop. Succulents such as cacti store water in swollen, waxy-skinned stems, reduce their leaves to spines (cutting water loss and deterring thirsty animals), and spread shallow roots wide to grab any surface rain. Other plants send tap roots deep to reach groundwater, or survive the drought as seeds that germinate, flower and set seed in a matter of days after a rare downpour (drought- evasion ). Many desert plants space themselves out and release growth-inhibiting chemicals to reduce competition for the little water. Animals are mostly nocturnal or crepuscular , sheltering underground through the heat of the day and emerging in the cool; they gain water from their food, produce highly concentrated urine and dry faeces, and species like the camel tolerate large swings in body temperature to avoid sweating. Biodiversity is low but every organism is a masterpiece of specialisation.

Temperate deciduous forest

In the mid-latitudes (~40–60° N), in the moister maritime margins of continents, lies the temperate deciduous forest — the natural vegetation of much of western Europe, the eastern United States and eastern Asia, and therefore the biome most heavily altered by human settlement. The climate has four clear seasons: warm summers, cold (but rarely severe) winters, and rain spread through the year. The signature adaptation is right there in the name: broadleaf trees such as oak, beech, ash and maple shed their leaves in autumn to survive winter, when low temperatures and frozen ground make water uptake difficult and low light makes photosynthesis unprofitable. Dropping their leaves cuts water loss and prevents damage from snow and frost; the fallen leaves rot down into a rich, fertile…