An unmanned space probe was sent to Mars to check for signs of life on the planet. How could such a probe confirm the existence of life?

                                                            

Unit One: The Nature of Life

BIOLOGY

It is the study of living things

Characteristics of Life

Each living thing is called an organism

Organisms have the following characteristics:

1) Living things are highly organized and contain many complex chemical substances

2) Living things are made up of one or more cells, which are the smallest units that can be said to be alive

Organisms cont’d

Living things use energy

Living things have a definite form and a limited size

Living things have a limited life span

Living things grow

Organisms cont’d

Living things respond to changes in the environment

Living things are able to reproduce

Groups of living things evolve, or change, over time

Non-living objects may show one or a few of these characteristics but never all

There are some “borderline” cases: Viruses- can be stored like chemicals in a bottles

but when inside living cells, they will reproduce

(but they still don’t have all the characteristics of living things)

Life Processes

Living things carry out many different kinds of processes Nutrition Transport Respiration Synthesis and Assimilation Growth Excretion Regulation Reproduction

Many of these life processes are required for maintaining a constant environment within an organism despite its changing external environment

The condition of a constant internal environment is known as homeostasis

Nutrition

All organisms take materials from its external environment and changes it into a more usable form

Nutrients are the substances that an organism needs for energy, growth, repair or maintenance

Taking in food from the environment is ingestion

Digestion is the breakdown of food materials into simpler forms

Transport

This is the process by which substances enter and leave cells and become distributed within the cells

Transport varies between single celled organisms and multi-cellular organisms Ex. Circulatory system in humans

Respiration

All life processes require a constant supply of energy

Respiration deals with energy released within cells

This may or may not involve breathing

Synthesis and Assimilation

Synthesis is when organisms are able to combine simple substances chemically to form more complex substances

Synthesis produces materials that can become part of the structure of an organism

It also allows the organism to `grow The incorporation of materials into the

organism’s body is called assimilation

Growth Growth is the process by which living

organisms increase in size

This is one of the results of the assimilation of nutrients

Growth in animals usually follows a pattern and will end

Some plants will continuously grow

Excretion

All organisms produce waste

Waste, if accumulated, can be harmful to the body

Removal of wastes is excretion

Regulation

All activities that help to maintain an organism’s homeostasis make up the process of regulation

Ex. Digestive system

Ex. Nervous system

Ex. Excretory system

Reproduction

This is the process by which living things produce new organisms of their own kind

2 types: Asexual (single individual produces offspring

identical to the parent)

Sexual (2 parents and offspring are not identical to either parent)

Metabolism

All the chemical reactions occurring within the cells of an organism are called its metabolism

This includes processes that build up complex substances from simpler ones and breaks down complex substances into simpler ones

Questions

How are humans and crystals, such as those that form on a window, alike in terms of their signs of life? How are they different?

Looking at the pictures shown previously, list all the characteristics that prove an organism is living. (rock, plant, mouse, paramecium, dead tree, cockroach, kitten)

Questions

List 4 ways in which a car is like a living thing. List 4 ways a car is not a living thing.

In PAIRS ONLY- create a mnemonic device that will help you remember all 9 life processes

Ex. Planets- My Very Eager Mother Just Served Us Nachos