Download File - Flipped Out Science with Mrs. Thomas!

Mission to Mars – Day 4
Defining Life
Remember this quote?
Mark Watney: If the oxygenator breaks down, I'll suffocate. If the
water reclaimer breaks down, I'll die of thirst. If the hab breaches,
I'll just kind of implode. If none of those things happen, I'll
eventually run out of food and starve to death.
We have some idea of what we need to do keep us
alive – but how do we know if something is alive to
start with?
If you went to Mars…the Viking Lander did!
• The primary mission objectives were to obtain high resolution images of
the Martian surface, characterize the structure and composition of the
atmosphere and surface, and search for evidence of life.
• If you went to Mars as an explorer, and your purpose was to find life –
how would you know what to look for?
• Make a list of criteria with your group right now of what identifies
life – you will share these ideas in a few minutes
• From these shared ideas, we will make a class definition of life.
What is life? (the Characteristics of Life)
• You are about to get a list of 8 characteristics that scientists have
found that help to define life (on Earth)
• Remember to keep an open mind – although these define life on
earth, do these define life everywhere?
1. Made up of one or more cells
• Unicellular (onecelled)
- ex. bacteria
• multicellular (manycelled)
- ex. animals, plants
2. Use energy to survive
• autotroph – makes its
own food using energy
from sun
• heterotroph – gets energy
by consuming other
organisms
3. Respond to stimuli in their environment
• Stimuli - factors in the
environment that living
things react to
• Response – the reaction to
something
• For example: If the plant
sense the dragonfly, it will
snap close, if the man
touches a hot pan, he lets
go.
• More ex:
light, hunger, temperature,
sound, fear
4. All living things reproduce
• sexual - two parents
required (sperm and
egg)
• asexual - only one
parent cell is needed
5. Grow and Develop
• Each cell divides to make new cells (cell division) – results
in growth
• Some cells become specialized and perform different jobs
than others (differentiation)
6. Maintain homeostasis
• Homeostasis –a term that is used to both describe the
survival of organisms in an ecosystem and to describe the
successful survival of cells inside of an organism.
• a relatively stable internal environment (within a certain
range)
- (ex. Human body temperature is
about 98.6 o F)
If you get too cold – what happens?
What if you are too warm?
Homeostasis video
7. Have a universal genetic code
• All living things have DNA (or
RNA)
• DNA – Deoxyribonucleic acid
• RNA – RibonucleicAcid (left)
• Both of these are ways to
carry genetic information
• DNA passes on genetic
information from one
generation to the next
8. Adapt and change over time to better
survive
• Evolution - gradual change
in a population of
organisms over time
• Individuals DO NOT evolve
Brain Break!
• How Life Began – Theory video
Now, let’s go back to the idea of what is life – the very basic form of life is what?
All living things are made of cells
• A cell is the simplest structure of living things
• If an organism is unicellular, all functions of life
happen within that one cell.
• If an organism is multicellular, the different cells
have different jobs and they all work together
Simple Organisms
• Some organisms are simple: they are not
particularly specialized and complicated in
structure (think microscopic)
• These cells are organisms that function
independently
For example: Bacteria, Archaea,
most protists (unicellular)
Complex Organisms
• Some organisms are more complex:
• “Complex” means that different parts of the
organism performs different functions.
Examples: humans, dogs, fish, mushrooms, oak
trees, etc.
Organization in a complex organism:
• Structure and function work together
• Structure is the way something is made, function is the
job it performs
• Structures join together to form systems
• Systems have specific functions due to the interactions
between the parts
• At each level of structure, the interaction among the
systems become more complex and more functions
become possible
Complex organization “order”
• Cells – form tissue
• Tissue – made of similar cells
doing a single job
• Organ – different kinds of tissues
that work together
• Organ system – a group of organs
working together
• Complex organism
• Then remember that this single
organism is part of a population,
community, ecosystem and biome!
Growth of an organism
• How do living things grow?
• Organisms grow by adding (making) more cells,
not by increasing the size of their cells
What do cells look like?
• The word “cell” is Latin for “small room”
• They look as varied as the organisms they build (make up)
Red Blood cell
Stem Cell
Brain cell
Plant cell
Cells have structure and function
• Within the cell, there are parts that each have
jobs or functions
• These parts or structures are called organelles
• Examples of organelles:
The microscope led to the
discovery of cells
A. 1665 – Robert Hooke published a book that described
the cell
1. He looked at cork (a plant) under the
microscope (30x)
2. He noticed little compartments, which he
named “cells” because they resembled the little rooms
that monks lived in
 B. 1675 – Anton Van Leeuwenhoek is
considered the father of microscopy because of
the advances he made in microscope design and
use.
1. He looked at pond water under the
microscope (300x) and noticed that the water
was full of moving living things
2. He made the most advanced microscope
of his time
The “Cell Theory” was created!
• With the invention of the microscope and
the contributions of many scientists, a
very important question was answered in
the 1850’s. The question was:
• Where do cells come from? – the answer?
Cell Theory
Forward Thinkers…
The Cell Theory was developed from three German scientist's
discoveries. They are Matthias Schleiden, Theodor Schwann,
and Rudolph Virchow.
In 1838 the German Botanist Matthias Schleiden discovered
that all plants were composed of cells. Then only a year later
a German zoologist, Theodor Schwann, discovered that all
animals were composed of cells. Later in 1855 a German
physician named Rudolph Virchow was doing experiments
with diseases when he found that all cells come from other
existing cells.
Schleiden
Schwann
Virchow
Cell Theory
There are 3 main concepts:
1. All living things are composed of cells
2. Cells come from other (pre-existing)
cells
3. Cells are the basic structure of living
things
More has been added:
The modern version of the Cell Theory includes
the ideas that:
• Energy flow occurs within cells.
• Heredity information (DNA) is passed on from cell
to cell.
• All cells have the same basic chemical
composition.