Living on Earth: Living Things and Ecosystems

What it means to be alive

Biology begins with three questions about the living world: what makes something ALIVE, what living things are BUILT FROM, and how they all DEPEND on one another. ⭐⭐ All living things share a set of life processes. A common way to remember them is MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition. A thing that does all of these is alive. ⭐ Living things are BUILT UP from tiny units called CELLS. Cells of the same kind group into a tissue, tissues form an organ, organs work together as an organ system, and the systems together make the whole organism. Small parts build into a working whole. ⭐⭐ No living thing survives alone. In an ECOSYSTEM, plants (producers) make their own food using light, animals (consumers) get energy by eating others, and every organism depends on the others and on its environment. This is INTERDEPENDENCE. This module is the living, biology strand of Unit 1. Matter and materials, the chemistry strand, has its own module. ⚠️ Carry one question the whole way through: is this about what makes something alive, what it is built from, or how it depends on other living things?

Alive, built up, connected

The three big ideas of the living world. Read across each one.

Tap the two life processes

Tap the TWO that are life processes, things all living organisms do.

• Respiration, releasing energy from food inside cells.
• Reproduction, producing new offspring.
• A nail rusting slowly in the rain.
• A candle burning and giving off light.

Alive or not

A car uses fuel, moves, and gives off exhaust gases, yet biologists do not call it alive. Which best explains why?

• It does only some life processes; a living thing does all of MRS GREN, including growth and reproduction from cells
• Because it moves, and living things never move
• Because using fuel means it cannot be alive
• Because only green things can be alive

The words biology starts with

Six terms this topic turns on. Learn them and living things read clearly.

Pair each term with its meaning

Two true things about living things

Select the TWO statements that are true.

• Cells group into tissues, tissues into organs, and organs into systems
• Producers such as green plants make their own food using light
• Every living thing is made of exactly one cell
• Living things survive completely independently of each other

Answering a living-world question

Strong answers use the right level of organisation and link living things to one another. ⭐⭐ NAME THE RIGHT LEVEL. Do not muddle a cell, a tissue and an organ. A cell is the basic unit, a tissue is similar cells together, an organ is tissues doing a job. Using the correct level shows real understanding. ⭐ CHECK FOR ALL THE LIFE PROCESSES. Before calling something alive, run through MRS GREN. A thing that does only one or two, like a moving car, is not alive; a living thing does them all and is built from cells. ⭐⭐ SHOW THE CONNECTIONS. In an ecosystem, trace how energy passes from producers to consumers, and explain how removing one organism affects the others. Interdependence is where the best marks are. DO NOT DRIFT INTO THE CHEMISTRY STRAND. Matter and materials has its own module; here, keep the focus on living things and how they connect. Describe processes in words, not as chemical equations. ⚠️ A note on accuracy. This is a new specification, so check the exact content list against the published specification; the ideas here are the standard, settled biology of living things and ecosystems. Keep the one question to hand: is this about what makes something alive, what it is built from, or how it depends on others?

Order the levels of organisation

Put the levels that build up a living thing into order, from the smallest to the largest.

• Cell: the basic building block
• Tissue: a group of similar cells
• Organ: tissues doing a job, such as the heart
• Organ system: organs working together
• Organism: all the systems making the whole living thing

Build a point about living things

Assemble one sentence that links the levels of a living thing correctly.

The living-world run

Five quick decisions about living things and ecosystems. Three lives.

Building a house from bricks

Leave biology aside for a moment. Think about how a house is built up from the smallest parts, and how, once finished, its parts all rely on one another. ⭐ You start with single bricks. Many bricks of the same kind, laid together, make a wall. Several walls together make a room. A set of rooms together makes the whole house. The tiny unit builds up, step by step, into a large working whole, and you can name each level in between. ⭐⭐ Once people live there, nothing stands alone. The lights need the wiring, the taps need the pipes, the heating needs both power and water. Take one system away and the others struggle: cut the water and the kitchen and bathroom both stop working. Everything leans on everything else. So a house shows two ideas at once: small identical units build up through named levels into a whole, and inside that whole the parts are linked so tightly that they depend on one another to work. ⚠️ Hold that picture. A living thing is built and connected the very same way: small units build up level by level, and every part depends on the others and on its surroundings.

Finish each living-world line

The basic building block that all living things are made of is the _____. A group of similar cells working together is a _____. Several tissues working together to do a job, such as the heart, is an _____. A green plant that makes its own food using light is a _____. An organism that gets its energy by eating other organisms is a _____.

Three living-world puzzles

Three situations are described. For each, choose the best scientific reading.

• A student argues that a river is alive because it moves and carries things along.
• In a meadow, grass is eaten by rabbits, which are eaten by foxes, and a disease then wipes out most of the rabbits.
• A learner labels the heart as a tissue.

Explain the living world

Explain the biology of living things: what makes something alive, how cells build up into organs and whole organisms, and how organisms depend on one another in an ecosystem. Give an example of interdependence. Describe processes in words, not equations.

• Explain what makes something a living thing (the life processes)
• Explain how cells build up into tissues, organs and organisms
• Explain the difference between a producer and a consumer
• Explain what interdependence means in an ecosystem
• Give an example of how losing one organism affects others