How do scientists look for life in the universe?

Images and activities adopted from NASA Astrobiology Institute

- Life on earth …and elsewhere?

You are an explorer in the future. You have discovered the remains of an unknown organism. You are particularly interested in knowing the origins of the new species and the mechanisms that led to its evolution.

PERFORMANCE TASK

You will appear before your colleagues (fellow explorers) to present your discovery.

http://www.newscientist.com/article/mg20727740.201-found-worlds-oldest-animal-fossils.html?DCMP=OTC-rss&nsref=life

http://www.cbc.ca/technology/story/2010/08/18/sponge-fossils-animal-australia.html

The Search for understanding our Identity continues…

What is Life?A. FlameB. Tree vs. pencilC. Real grass vs. artificial grass

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

http://www.s-cool.co.uk/gcse/biology/cells/characteristics-of-life.html

Quick Review:

• Made up of cells

• Obtain and use energy from the environment They also require liquid water.

• Grow and reproduce

•Maintain a state of balance. They have a membrane or wall that creates an internal environment • Carry out processes resulting in the exchange of gases and solid materials (example: using raw materials and producing wastes)

• Able to respond to its environment, adapt and evolve.

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

All living things...

Images from http://library.thinkquest.org

There is no firm scientific definition of life, no single test that can establish the presence or absence of life, and no single characteristicthat applies to all living things.

• There are characteristics that almost all living creatures share.

• Two characteristics useful in helping distinguish life from non-life are the ability to reproduce and the ability to produce and perpetuategenetic variation among offspring.

ACTIVITY 1: EVIDENCE OF LIFE

Which of these two samples: powder and blob are living? Why?

Sample A: Powder Sample B: Blob

To find out: Place the 2 samples in water. Observe.

Note: Organize a notebook page. Write answers in your notebook.

ACTIVITY 1: EVIDENCE OF LIFE

Focus Question: Why do you say that the sample is living? How did ‘life’ develop from ‘non-life’? Provide a possible explanation.

Activity:

1.Prepare a wet mount of the sample.

2.Observe the specimen under Low power, then High power objective.

3. Draw one organism following the guidelines on Making Biological Drawings.

MAKING BIOLOGICAL DRAWINGS

Name of Specimen: ________________________ Source: __________________________________ Magnification: ___________________________ Description: (physical characteristics) _________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Specimen 1

Lines parallel ; labels are ruler

drawn and right hand side

SAMPLE- Detailed drawing

Self-assessment: Practice drawing

Assessment 1. Making Biological Drawings

1. Prepare a wet mount of the sample.2. Locate and observe one organism.3. Draw an organism following the guidelines on biological drawings.

LIFE The Most Basic Needs

MAKING PREDICTIONS: Predict what might grow in these given situations.

Many astrobiologists use the availability of liquid water as the primary criterion for judging whether a planet is a candidate for life. While other liquids do exist (e.g., ammonia, methane, or ethane), they exist at temperatures far below the level conducive for life.

The life discovered to date seems to be limited to a temperature range of about minus 15°C to 115°C. Under the right conditions, water can be liquid over this entire range.

WATER

All life requires energy. Organisms use either light energy or chemical energy to run their life processes. Light energy is available only to organisms that live on or close to a planet or moon’s surface. For life to exist there, the surface must be within a temperature range conducive for life and be protected from harmful ultraviolet radiation and charged solar particles.

Organisms that live beneath the ground depend on chemical energy for their needs.

ENERGY

Nutrients are the raw materials organisms need to construct and maintain their bodies. While the solid planets and moons in our solar system all have the same general composition, local conditions and processes have led to variations in the concentrations and availability of different chemical compounds. As a result, nutrients required by life are more available on some planets and moons than on others. Atmospheres can also serve as a source of nutrients. For example,nitrogen from nitrogen gas can be used to make proteins and carbon from carbon dioxide or methane can be used to make carbohydrates and fats.

NUTRIENTS