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Concept Sheet
Basic Needs and Processes of Life
LS.2: The student will investigate and understand that all living things are composed of cells.
1. An organism is a living thing. You, a dog, a tree, a fish, a mushroom, an amoeba, a spider, a flower and so on all
have six things in common that distinguish them as living. All living organisms:
- have cellular organization (are made of cells)
Remember this:
- contain similar chemicals (all life on Earth is carbon based. The
Living things must be able to do
four most abundant elements in all living things are carbon,
ALL six of these things
hydrogen, oxygen and nitrogen)
independently. This is why viruses,
- use energy (producers, aka autotrophs, are able to transform the
which exhibit many of the
electromagnetic energy of the sun into chemical energy that
characteristics of life, as NOT
they and other living things can use)
living, because they cannot
- respond to their surroundings (even plants respond to their
reproduce without a living host cell.
surroundings. Phototropism, growing toward the light, is a
plant responding to the location of the light source)
- grow and develop (the process of mitosis allows organisms to grow, heal and develop)
- reproduce (asexual and sexual reproduction are two ways organism reproduce. Sexual reproduction relies
on meiosis)
There are two main types of cells, prokaryotic, cells without a nucleus, and eukaryotic, cells with a nucleus.
Prokaryotic cells are found in single celled organisms, while eukaryotic cells can be found in both single cellular
and multicellular organisms.
2. All living things are made up of one or more cells. The cell is the basic unit of all life. Each cell is made up of
organelles, which are small structures that perform a specific function within the cell. Many organelles are
visible with a basic compound light microscope, like the ones we’ve used in class. In general, plant and animal
cells have many, but not all, of the same organelles.
Major Organelles in Plant and Animal Cells
Organelle
Function
Type of Cell
Controls all activities in the cell and stores DNA. A big substructure in
Nucleus
Animal and Plant
the nucleus is the nucleolus, which is where ribosomes are made
Vacuole
Stores water, food and waste products
Animal and Plant
Performs cellular respiration, the process of releasing energy for the
Mitochondria
Animal and Plant
cell to use – “powerhouse”
Endoplasmic
Provides a pathway to move materials around the cell. Two parts,
Animal and Plant
Reticulum (ER)
smooth ER and rough ER. Rough ER has ribosomes attached to it
Gel-like substance (80% water) in which the other organelles are
Cytoplasm
Animal and Plant
suspended
Allows certain materials in and out of the cell. It is selectively
Cell Membrane
Animal and Plant
permeable, acting like a screen on a window
Lysosome
Contains digestive enzymes to break down materials
Animal and Plant
Ribosome
Build proteins
Animal and Plant
Golgi Apparatus
Packages materials to be used in other places in the cell or in other cells Animal and Plant
Cell Wall
Provides structure for plant cells. Surrounds the cell membrane
Plant
Site of photosynthesis. Contains chlorophyll, the green pigment that
Chloroplast
Plant
give plants their green color.
3. All cells are structured, shaped, in a way to help them function best. For example, red blood cells are very small
and flexible to fit through capillaries, which can be as small as one cell thick. Nerve cells can be very long. The
longest nerve cell in humans is 3-4 ft long! This is short compared to nerve cells in organisms like blue whales.
In general, animal cells tend to be more round in structure, as this makes them more flexible and better to move
and react quickly to the environment. Plant cells, in contrast, tend to be rectangular shaped. This is due to the
more ridges cell wall found in plant cells. This makes stacks of plant cells more stable and strong.
4. Robert Hooke used a type of microscope to observe a piece of cork and discovered compartments that he named
cells. Anton van Leeuwenhoek is credited as the first person to make a simple microscope and with it he
observed single celled organisms which he called “animalcules”. These discoveries laid the groundwork to help
others research cells. Cell theory is the accumulation of the work of many scientists, but the three credited with
its development are Schleiden, Schwann and Virchow. Cell theory states:
- All living things are composed of cells
- Cells are the basic units of structure and function of living things
- All cells are produced from other cells
5. Cells are continually growing, repairing dead cells within an organism. Cells do this through a process called the
cell cycle. Most of a cells time is spent in interphase; when the cell is growing and copying its DNA to prepare
for replication. The
second stage of the cell
cycle is mitosis. Mitosis
creates two new cells
that are an exact copy
of the original cell. It
has for stages:
prophase, metaphase,
anaphase and telophase.
This leads to the stage
of the cell cycle is
cytokinesis, which is
when the cell pinches in
the middle and
Memory Trick:
separates to form two
To remember the steps of mitosis think “I Peed on the MAT, C? Puppies as
separate cells.
they grow up undergo lots of mitosis and don’t pee on your rug as much.
The process has to be modified slightly to make sex cells (sperm and eggs) for sexual reproduction. The process
is called meiosis (my-oh-sis). The original cell creates four daughter cells instead of two. Each cell also has half
the number of chromosomes as the original cell. For example, humans have 46 chromosomes in their normal
cells. Sperm and egg cells only have
Memory Trick:
23 chromosomes. So when the sperm
To remember the difference between mitosis and meiosis, remember that
and egg combine, the resulting
your toes look about the same so mitosis is replication and growth. And
offspring has 46 chromosomes as
meiosis is for sexual reproduction because “my, oh my, what a cute baby!”
well.
LS.3: The student will investigate and understand that living things show patterns of cellular organization.
6. Cell are the basic unit of life. Unicellular organisms are made up of just one cell. Bacteria are an example of
unicellular organisms. Multicellular organisms are made up of many cells. Animals are examples of
multicellular organisms.
Cellular Organization in Multicellular Organisms:
Cells  Tissues  Organs  Organ systems  Organisms
A group of cells that perform the same function, like a muscle cell, are organized
together to form a tissue, like a muscle. In multicellular organisms, different
tissues layer together to form an organ, like a stomach. Then different organs
work together to form an organ system, like the digestive system. Finally, many
organ systems working together form an organisms, like a mouse. An organism is
the most complex of the five levels.
7. Cells need to remove waste from cells, bring in food, as well as balance water and compound levels within and
outside the cell. One process of doing this is called diffusion, which is
the movement of molecules along a concentration gradient, so from an
area of high concentration to an area of low concentration. When it is
water molecules moving across a selectively permeable membrane, this
process is called osmosis.
Both diffusion and
osmosis are examples of
passive transport because they require no energy from the cell –
they occur automatically. There is another type of transport called
active transport that does require the cell to use energy because
it is moving molecules against the concentration gradient.
LS.4: The student will investigate and understand that the basic needs of organisms must be met in order to carry
out life processes.
8. Plants and animals both have basic needs. They need water, gases, food/nutrients (energy), habitat/shelter and
space. These needs need to be met in a balanced way. Having too much of one thing can be harmful, just as
having too little can also be harmful. For example, if an organism has too much space they will have a hard time
finding mates of the same species to reproduce; however if they have too little space, diseases can quickly
spread, wiping out the population.
9.
Some factors that influence the life processes include: the amount of sunlight, climate changes, and natural
catastrophes (like hurricanes, earthquakes and/or floods). Humans also affect ecology by building new homes,
roads and shopping centers; which destroy the natural habitats of many plants and animals and often increases
pollution of the air and water.
LS.6: The student will investigate and understand that the basic needs of organisms must be met in order to carry
out life processes.
10. All the energy in living things originally comes from the sun. Photosynthesis is the process used by producers,
like plants (also called autotrophs), to change light energy into useable chemical energy. Chlorophyll is a
chemical pigment found in the chloroplasts that absorbs solar radiation. The chemical equation below shows how
plants use carbon dioxide
and water as a reactant.
These molecules are
recombined using solar
energy to create the
products glucose (sugar)
and oxygen. The glucose
is stored in the plant cells
and the oxygen is released
into the air.
Photosynthesis is the foundation of virtually all food webs. When looking at energy
pyramids, the producers are at the base, which shows that most of the energy for an
ecosystem is found there. The energy stored in glucose is transferred to a primary
consumer, an animal that eats the plant. Then that energy is transferred again to a
secondary consumer, when another animal eats the first animal.
To release the energy stored in the chemical bonds of the glucose molecule it must be broken down. This process
is called cellular respiration and occurs in the mitochondria of living cells. The equation for cellular respiration
is the exact opposite of photosynthesis. Both plants and animals perform cellular respiration.