Characteristics of Life

Intro to Biology

Our Goals for Today:

Create a list characteristics of living things. Discuss the chemical composition of living

organisms Determine the relationship between living

things and non living things. Evaluate whether subjects of a case study

are living, non living, or some other category

Composition of LifeLet’s think about what living things are made out of.All organisms, no matter how strange they look, are

built from the same building blocks:

Proteins

Lipids

Carbohydrates

Nucleic Acids

• Muscle fibers• Enzymes• Antibodies

Proteins

• Fats and oils• Cholesterols• Cell membranes

Lipids

• Sugars• Starches• Cellulose

Carbohydrates

• DNA• RNANucleic Acids

• They each contain atoms of carbon

What do each of those molecules have in common?

• All living things on Earth contain carbon

We are carbon based life forms

• Carbon is like the really cool lego in the building set. You can attach so many things to it! Carbon can make really big complex molecules necessary for living things.

Why carbon?

Characteristics of Living Things

All living things have a similar compositions.What else do they have in common?

Characteristic #1complex organization, made of cells containing

DNA

HAVE CELLS AND DNA

• Multi-cellular: cells differentiate from a single fertilized egg cell, and they just “know” to become a heart, leg etc.

• Uni-cellular : one celled organism (amoeba or bacteria)

• Both above have DNA ( the genetic code: which is why we look like our parents)

Characteristic #2

• have motility and can respond to the environment

• Stimulus- signal to which an organism responds – Response- (what they do because of the signal)

• Internal stimulus- ex.) sugar levels drop? …then you feel hungry

• External: ex.) flower leans toward the window in a classroom

Characteristic #3 reproduce

Reproduce

• There are 2 types of reproduction:• Asexual : 1 parent (budding) - identical– bacteria

• Sexual: 2 parents– cats– people

Characteristic #4

Living things grow and develop

Growth and Development

• Bacteria- grow, they just increase in size• People – develop … they increase in size and

their bodily functions change over time….until they become an adult

• ex) puberty…

Characteristic #5

• Populations of organisms can mutate and evolve from one generation to the next

• 100,000’s of millions of years…changes can be dramatic within a species…

• ex) pre-historic horse was the size of a Barbie doll horse

Characteristic #6• Living Things Need and Use Energy

Living things use energy to grow/develop/reproduce… or just stay alive

• Where do we get energy from? • Metabolism: combination of chemical

reactions through which an organism builds up and breaks down materials (will release energy) as it carries out life processes– Fast metabolism- break down – Slow metabolism – store for later

Where are they getting energy from?

How obtain energy?

• Plants: From the sun’s energy “photosynthesis”

• Lion: From eating other organisms “herbivore, carnivore”

• Mushroom: From the remains of dead organisms (decomposers)

7. Maintain Homeostasis

7. Maintain Homeostasis

• External: conditions may vary widely• But internal…. Should be kept constant.. This is

homeostasis • Ex) temperature 98.6 F, water content, etc • Ex of how it happens? – Shivering/sweating – Thirst/feeling of fullness

Complex organization based on DNA-one or

more cellsResponse to environment

Reproduction

Growth and development

Mutations and evolution

Need and Use Energy

Let’s Review

Maintain Homeostasis

HomeworkDue: Thursday, September, 3

• You will create a product to summarize what you have learned about the 7 Characteristics of Living Things– Personal Choice– Must Include lots of color if doing anything visual– Must have approval from Teacher– Possible Products:

• Poem or song• Book mark• Children’s book• Poster

Case #1: Journey to Europa

Journey to Europa

It is 2113. You are a xenobiologist traveling with a crew of astronauts to Europa. It has long been thought that Europa could support living organisms. Your mission is to gather samples and analyze them for the presence of alien life.

Arrival

Your shuttle arrives on the Galilean moon’s surface, a cold and barren place. It is -370⁰F, and the radiation that burns through the moon’s thin atmosphere makes it terribly dangerous to step outside.

As the shuttle sets down, you and the crew look out through the view ports. It is the only close up view you will have of the moon’s surface. No one is allowed out. All of your work will be done under the protective hull of the ship.

DrillingOnce the shuttle has secured itself to the

surface, its drill is activated. Europa’s ice crust is thin, and it only takes

..a few hours before the first .samples are brought up.

Water!Under the ice is an ocean! Finally, after over a

century of speculation, we now know that the tidal forces from Jupiter have kept the moon’s core warm enough for liquid water.

Samples

Before cameras and submersibles can be deployed, the first set of samples are brought up for analysis, and there is no time to lose.

Sample #1The first water sample reveals tiny particles.

After analysis, these particles appear to have the following characteristics:

• Complex boron based molecules, but no DNA or RNA• Mobility• Response to light and temperature stimuli• No observable reproduction after 2 days• Uptake of sulfur and boron “nutrients”• Production of nitrogenous secretions

Sample #2The second sample shows a filmy substance that

collects at the surface of the water. Further analysis shows the following characteristics:

• A lipid bi-layer membrane similar to our own cells• Organic molecules such as carbs and amino acids inside the membrane bubbles• No observed reproduction after 2 days• No DNA or RNA• No response to external stimuli• No gas exchange or nutrient uptake

Case #2: A Mysterious Plant Illness

A Diseased Tobacco CropYou are a botanist studying the spread of disease

among tobacco plants. Crops have been failing extensively, and tobacco farmers are desperate for a cure. Nothing seems to be working!

What Could it be?

You obtain some infected plants for further analysis and head back to your lab.

Where is the Pathogen?

You crush up the leaves and examine the fluids under a microscope. There are several different types of bacteria, but all of the ones you see are common and not known to cause disease.

The Chamberland Filter• You decide to pass the fluids through a

Chamberland filter, a special apparatus with holes that are tinier than bacteria. The fluid should pass and leave all bacteria behind.

A Tiny DiseaseThe fluid no longer has any bacteria. You take a

closer look. The microscope reveals that the fluid is perfectly clear. However, when you drop the fluid onto healthy tobacco leaves, they become sick. There is something in that fluid!

An Even Closer LookYou decide to send the samples to be analyzed

by a more powerful microscope. You only have a light microscope, and you need an electron microscope to get a closer look.

The Results Are In!An electrograph is sent back to you. In the

image, you see strange, rod-like particles.

Structure of the Mystery ParticlesThese particles are highly organized. They are

composed of proteins, and each have a strand of their own hereditary information in the form of RNA.

How Strange!The particles do not appear to be able to

reproduce on their own. Yet, when they are placed on living plant cells, they inject their RNA into the plant and force it to make new mystery particles! In this way, they are literally hijacking the tobacco cells and causing them to die while the particles reproduce and spread.

Are they alive?

What are these strange things? You decide to probe further. In your studies you learn:• they do not respond to outside stimuli. • they do no appear to grow or develop once they are

assembled by the tobacco plants. • they do not need nutrients or oxygen or carbon

dioxide. • but, after trying various treatments you notice that

resistant particles evolve. The genes in the RNA must be mutating!

So what is it?

It’s a type of virus!Viruses are not considered living things, but they

share a lot of characteristics with life.