1. 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?

9. Unit One: The Nature of Life

10. BIOLOGY
It is the study of living things

11. 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

12. 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

13. 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

14. There are some “borderline” cases:
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)

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

16. 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

17. 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

18. 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

19. Respiration All life processes require a constant supply of energy
Respiration deals with energy released within cells
This may or may not involve breathing

20. 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

21. 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

22. Excretion All organisms produce waste
Waste, if accumulated, can be harmful to the body
Removal of wastes is excretion

23. 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

24. 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)

25. 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

26. 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)

27. 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