CELL DIVISION/MITOSIS

What is mitosis?

Mitosis is a cell division that produces two daughter cells which are identical (the same) or when the cell makes an identical copy of itself

Cells that are produced by mitosis are identical in chromosome number and in chromosome combination. An example is below:

Parent cell                                                              Daughter cells





Why do cells undergo mitosis?

• Some cells use mitosis as a means of reproduction. For instance, single-cell organisms reproduce by mitosis. This is a form of asexual reproduction where the genes come from one parent.
• There are some multicellular organisms that are able to use mitosis as a means of reproduction.
• Multicellular organisms use mitosis for growth.
• Mitosis is also used to replace injured cells and dead cells. 
• In humans after the egg is fertilized, mitotic cell division is used to make all of the structures that are necessary for a human to function (heart, brain, legs...)

MITOSIS POWER POINT PRESENTATION
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MITOSIS Animation
Want to learn more about mitosis? Check out the links below!


MITOSIS TUTORIAL

MITOSIS IN A PLANT CELL
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What are the types of cell division?

1. mitosis
2. meiosis
3. binary fission.
   

Why do cells divide?

• Cells divide for growth
• Cells divide to replace injured cells, for instance when you cut yourself.
• Cells divide to replace old cells that died
  
  

What about humans and other multicellular organisms?

• All of the body cells found in humans and other multicellular organisms are made by mitosis.
• For instance, your skin, your bones, liver, lungs, hair etc.. are all products of mitosis.
• These cells do not look alike and do not have the same functions but they are identical in chromosome numbers and chromosomes combination.

How is it possible that cells with same DNA do not look identical and do not have the same function?

• The DNA refers to all of the organism's genes. However, some genes are active in some cells and not active in others. For example, the bone cells have the gene for becoming a skin cell, but they do not activate this gene; instead, they focus on the gene that will allow them to become a bone cell.
• This concept of becoming a task specialist is called differentiation.

How would humans be different, if we were to reproduce by mitosis?
Compare the advantage to the disadvantage of reproducing by mitosis.
How can you use this information?
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Want to learn more about mitosis? Check out the links below!MITOSIS TUTORIAL MITOSIS IN PLANT CELL
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Make a connection:Binary Fission is similar to mitosis, it produces two identical cells. This type of cell division only occurs in bacteria

DON'T FORGET!

• Cells produced by mitosis may not look alike, but they are identical in chromosome numbers and combination.
• Mitosis produces two genetically identical daughter cells.
• Organisms that reproduce asexually, reproduce by mitosis

CANCER IS UNCONTROLLABLE MITOSIS
Cancer cells continuously divide and do not undergo cell death.
Why do you think that cancer usually causes people to lose weight?
To learn more, click this link. CANCER MOVIE

Use this hands on game to help deepen your understanding of mitosisMITOSIS INTERACTIVE

BACK TO TOPICS

CELL DIVISION/MEIOSIS

What is meiosis? 

or 

What are the characteristics of meiosis?

1. Meiosis is a cell division that produces the sex cells or the gametes. (for example: the sperms and the eggs)
2. Meiosis produces four daughter cells that are NOT IDENTICAL (not the same).
3. Sometimes meiosis is referred to as the reduction of the chromosomes because cells that are produced by meiosis have half the number of chromosomes as the parent cells.

Meiosis

Parent cell

 Four daughter cells

1. How are these daughter cells similar to each other? 
2. How are they different from each other?
3. How do they compare to the parent cell?

Note: 

• Only  sex cells are produced by meiosis

• Meiosis only takes place in the testis of males and ovaries of females

 

For more information, click on this:

MEIOSIS POWER POINT PRESENTATION

List three events that occur in meiosis that are responsible for diversity in sexually reproducing organisms.

• Crossing-over
• Independent assortment
• Two consecutive cell divisions

What are sex cells?

• Sex cells or gametes are the sperms and the eggs.

• These cells have half the number of chromosomes as the body cells.

• Additionally, each of the sperm cells or the eggs has a different combination of chromosomes to each other.

• The male sex cells or sperms are produced in the male testis, and the female sex cells or eggs are produced in the ovaries

-How are sperm cells different from egg cells?

-How are they similar?

LOOK AT THESE SPERM CELLS!

CHECK OUT THIS EGG CELL!

Where do you get your genes from?

• You inherit (get) your genes from your parents.
• You receive half of your genes from your mom and the other half from your dad.
• The sperm brings the half from your dad and the egg brings the half from you mom.

If you and your siblings are receiving genes from the same parents, how come you are not identical?

 

HEREDITY:
IS THE PASSING OF TRAITS FROM PARENTS TO OFFSPRING

NOTE:  CELLS PRODUCED BY MEIOSIS EACH HAS A UNIQUE COMBINATION

• For example, each time a man ejaculates, he releases 3 million to 5 million sperms and each sperm has a slightly different combination.

Why do you think it is necessary for a man to release so many sperms?

How are cells produced by mitosis different from cells produced by meiosis?

• In cells produced by mitosis the chromosomes are in pairs.

• In cells produced by meiosis the chromosomes are not in pairs.

Learn more here:

Mitosis vs Meiosis Animation

 

Learn even more here!MITOSIS VS MEIOSIS 2

 

What are three types of reproduction?

1. Asexual reproduction
2. Sexual reproduction
3. Cloning.

How is a asexual reproduction different from sexual reproduction?

• Asexual reproduction involves just one parent and the offspring are identical to the parent.

• Sexual reproduction involves two parents and the offspring are similar, but not identical either parent.

• What are some advantages of sexual reproduction?
• What are some disadvantages of sexual reproduction?
• What are some advantages of asexual reproduction?
• What are some disadvantages of asexual reproduction?

What are 3 types of asexual reproduction?

1. fragmentation
2. binary fission
3. budding.

Fragmentation
Occurs in star fish. For instance, if you step on a star fish and break in four pieces, as long as each part contains portion of the nucleus, each part of the star fish will become a new organism.

Budding
Some organisms like certain plants are able to form a bud. This bud can fall to the ground and grow to become a new plant.

Binary fission
A process similar to mitosis that bacteria use to reproduce

What is FERTILIZATION?

• Fertilization is the union of the sperm and the egg. Zygote is the new cell that is formed by the egg and the sperm.

What is cloning?

Cloning is a technique that produces the same end result as asexual reproduction.Cloning produces organisms that are identical. This procedure involves the removal of nucleus from one cell and placing it into another cell.

Is there an advantage to sexual reproduction?
Yes, Sexual reproduction creates differences or diversity. Because sexual reproduction creates so many different combination, when the environment changes, there is a better chance that some organisms will survive.

FOR INSTANCE, if two members of the same family are exposed to H1N1, however, it is possible that only one of them dies from the disease and the other member is not affected. If they were identical, if one dies, the other would also die. Sexual reproduction increases the chances for survival when there is change in the environment.

Is there a disadvantage to sexual reproduction? 

• You cannot guaranty the expression of the desirable trait.
• Undesirable recessive traits may be expressed.
• Produces less offspring
• Reproduces slower
• Requires two parents

Is there an advantage to asexual reproduction?

• Offspring are identical
• Requires only one parent
• Produces more offspring
• Reproduces much faster

Is there a disadvantage to asexual reproduction?

• Lack of diversity

REVIEW QUESTIONS

What is mitosis?

• Mitosis is a cell division that produces two daughter cells that are identical.

What is meiosis?

• Meiosis is a cell division that produces the sex cells or the gametes.

Where does meiosis occur?

• Meiosis only occurs in the male testis and the female ovaries.

How are cells produced by mitosis different from cells produced by meiosis?

• Cells produced by mitosis have a full set of chromosomes and cells produced by meiosis have half the number of chromosomes as the organism

In reference to evolution, what type of cell division came first, mitosis or meiosis?

• First, we must acknowledge that meiosis only occurs in sexually reproducing organisms. Since the first life forms were asexually reproducing organisms, meiosis is an evolutionary trait. Therefore, it is logical to conclude that mitosis came first.

Where does fertilization occur?

• Fertilization occurs in the fallopian tube or oviduct.

What happens after the egg is fertilized?

• The new cell, the zygote moves to the uterus where the baby will grow and develop through mitotic cell division.

The most important thing to remember about meiosis is:

• It reduces the chromosome number in half.
• It is one of the mechanisms responsible for the diversity or differences in organisms and that is because each sperm or egg created by meiosis is different.

THINK!
How would the world be different, if humans could only reproduce asexually?

QUIZ YOURSELF

BACK TO TOPICS

ECOLOGY (ORGANISMS AND THEIR ENVIRONMENT)

What is ecology?
Ecology is the scientific study of how living things interact with the environment

Autotrophs are producers and producers are organisms that make their own food (glucose). They are the only organisms that can convert solar energy into chemical energy or food (organic compound). They carry out autotrophic nutrition. Plants and algae are autotrophs.

Auto: means self

Troph: means feeder

Autotrophs: are self-feeders

PLANTS ARE AUTOTROPHS. (They make their own food)

ALGAE ARE AUTOTROPHS (They make their own food)

Scientists estimated that about 65 - 85% of the oxygen we breathe comes from algae.

Heterotrophs are consumers and consumers are organisms that eat or obtain nutrients made by autotrophs. They depend on autotrophs for food. Horses, cows, lions and humans are heterotrophs.

Herbivores are heterotrophs that eat plants only, EX. COWS .

A COW IS A HERBIVORE.

Carnivores are heterotrophs that eat meat only, ex. lions.

A LION IS A CARNIVORE.

Omnivores are heterotrophs that eat both meat and plants, ex. humans.

HUMANS ARE OMNIVORES.

Decomposers are organisms that break down dead organisms and return them to the soil. They recycle nutrients. Ex. of decomposers are fungi and bacteria.

MUSHROOMS ARE DECOMPOSERS. (mushrooms are fungi)

Predators are organism that kill other organisms for food, ex. a lion is a predator.

Prey are organisms that are killed and eaten by other organism, ex. deers are killed and eaten by lions. Deers are preys.

Scavengers are heterotrophs that eat dead organisms, Ex. vultures.

Biotic are living things. Ex. plants, humans, cows and mushrooms are biotic factors

Abiotic are nonliving. Ex. sun, water, oxygen and temperature are abiotic factors

Niche is the role that the organism play in the environment. For example, a lion's role is "predator"

Habitat is the place where organisms live.

Carrying Capacity refers to the maximum number of organism a habitat can support. Once the number of organisms reaches the carrying capacity, it levels out or stop growing.

Limiting Factors refers to any biotic or abiotic aspect of the environment that affect population growth. For example, in a desert, water and temperature are abiotic limiting factors; food, prey, and predator are biotic factors that can affect population growth.

Species Two organisms are of the same species if the can reproduce (make babies or offspring) and their babies are fertile. That is their babies can also make babies.

Population: Organisms of the same species living at the same place at the same time, for example a population of dogs, a population of cats.

Community: Different populations living at the same place and at the same time. For example, we live in a community made up of people, cats, dogs, trees, other animals and plants.

Ecosystem consist of the living and the nonliving

THINK! Provide an explanation that justifies that a person is a community.

The Food Chain And The Food Web show how energy moves through the ecosystem.

EXAMPLE OF FOOD CHAINEnergy for this food web comes from the sun.


NOTE: The arrow in the food chain or the food web represents energy. The caterpillar is receiving its energy from the flowers by eating them.

• What happens to the owl population if the snake population is removed from the food chain?

• How is the caterpillar population affected by the removal of the snake population?

EXAMPLE OF FOOD WEB

THE ORIGINAL SOURCE OF ENERGY FOR OUR PLANET IS THE SUN.

THINK!

• How is the rabbit population affected if the deer population is removed from the food web?

NOTE: In an ecosystem, the greater the biodiversity the more stable the ecosystem.

Between a corn field and a forest, which one is more stable?

What if the second level of the pyramid was larger than the first, how would that affect stability of the ecosystem?

Explain!


INTERACTIVE FOOD WEB 1

INTERACTIVE FOOOD WEB 2

INTERACTIVE FOOD WEB 3

-The first organism in the food chain or the food web is always a plant because only plants can convert sunlight into food.

-In the next level in the food chain or web are the herbivores because herbivores eat plants.

-Carnivores are found on the third level or higher because they eat herbivores or other carnivores.

The arrow in the food chain or food web represents energy

Energy decreases as it goes through the ecosystem because energy is used for life functions and energy is lost as heat.

- If you remove an organism from the environment, the environment becomes less stable.

- The greater the biodiversity, the more stable the environment.

NOTE: Anytime that you lose biodiversity, you lose genetic materials, food may lose predators or other organisms needed to maintain stability in the ecosystem

Questions

1. Why are plants at the bottom of the food pyramid?
2. What happens to energy as it goes through the ecosystem?
3. In the food web, how come no arrow is pointed toward the plant?
4. What is the role of decomposers?
5. Identify two organisms that carry out decomposition.
6. What does the arrow represent in the food web?
7. At what level of the energy pyramid would you find the largest amount of biomass?

Answers

1. Plants are at the bottom of the food pyramid because they can convert sunlight into food for animals.
2. As energy goes through the ecosystem it decreases because it is used by organisms for life functions and it is lost as heat.
3. Plants do not receive energy from other organisms.
4. The decomposers recycle nutrients, or break down dead organisms and return them into the soil so that they can be used by plants.
5. Fungi and bacteria carry out decomposition
6. In the food web, the arrow represents energy.
7. The largest amount of biomass is found at the bottom of the energy pyramid.

Remember

Living things depend on biotic factors such as food and abiotic factors like oxygen, soil, temperature, light and water.


Ecological succession refers to the orderly changes that take place in an ecosystem, where one group or organisms is being replaced by another.  The last stage is always the most stable.

Renewable resources are resources that can recycle themselves within a short amount of time. Example: trees, animals, humans, water, oxygen are renewable resources.

Nonrenewable resources are resources that cannot recycle themselves in a short amount of time, and therefore efforts must be made to conserve them. Fossil fuel like gasoline, coal and cooking gas are nonrenewable resources.

BACK TO TOPICS

Cell Organelles/Homeostasis

ALL LIVING THINGS ARE MADE OF CELLS.

The cell theory

• Cell is basic unit of living things.
• All organisms are made of cells.
• All cells come from other cells.

IMAGE OF PLANT CELL

IMAGE OF ANIMAL CELL

There are two BASIC CELL TYPES: eukaryote and prokaryote.


INTERACTIVE ANIMATION
OF
PROKARYOTE VS EUKARYOTE
 -Eukaryote cells have nucleus-
Prokaryote cells DO NOT have a nucleus.
ONLY bacteria are prokaryote.

Functions of some cells in eukaryote organisms(The roles that some of your cells play in the body)

• red blood cells carry oxygen to cells and carry carbon dioxide to the lungs.
• White blood cells fight germs like viruses and bacteria.
• Muscle cells specialize in contraction and are used for movement.
• Nerve cells carry nerve signals or nerve impulses that are used for communication.
  

Organelles are membrane bound structures found inside eukaryotic cells. (Little organs inside the cell)


HERE ARE SOME OF THE ORGANELLES FOUND INSIDE THE CELL.

THE NUCLEUS

Nucleus: Holds the DNA and directs or controls all activities. (found in both in plant and animal cells)

Nucleolus: makes ribosomes (located inside the nucleus)

THE RIBOSOMES

Ribosomes: make proteins or is involved in protein synthesis. (found in all cells) looks like dots

THE MITOCHONDRIA

Mitochondria: converts glucose and oxygen into a form of energy usable by the cell called ATP. (found in both plant and animal cells).  This is the structure where cell respiration occurs.

Cell respiration: is the process that occurs inside the mitochondria where glucose is converted into a form of energy usable by the cell called "ATP".

The formula for cell respiration is: O2 + glucose Change to: ATP + CO2 + H2O

THE CHLOROPLAST

Chloroplast: a structure found in plant cells that converts sunlight, carbon dioxide and water into glucose and oxygen. This process is called photosynthesis.
(found only in photosynthetic organisms, mostly plants)

PHOTOSYNTHESIS VIDEO

VIDEO OF PHOTOSYNTHESIS2

ANIMATION OF PHOTOSYNTHESIS3

The formula for photosynthesis is: Light + CO2 + H2O Change to: O2 + glucose

POWER POINT PRESENTATION OF CELL RESPIRATION & PHOTOSYNTHESIS

THE CELL MEMBRANE

Interactive Cell Structures and Functions

Cell Membrane: controls what goes in and out of the cell. (found in all cells).  It is able to to do that because it is selectively permeable.  That is, it has small holes. Therefore, small molecules such as water, oxygen and carbon dioxide are able to go through,while larger molecules must go through a protein channel.

CHECK THIS INTERACTIVE 

Cell Wall: structure that makes up the outside border of plant cells, which helps the cell maintain its shape. (found in plant cells)

THE VACUOLE

Vacuole: structure found in plant cells that stores materials. (found in plant cells and some animal cells)

Lysosomes: have digestive enzymes that breakdown things like bacteria, viruses and old organelles.

Golgi Apparatus: Is considered the post office of the cell. It receives, stores, modifies, packages and ships newly synthesized or newly made proteins to different destinations in the cell. VIDEO OF THE GOLGI

THE ROUGH ENDOPLASMIC RETICULUM

Rough Endoplasmic Reticulum(RER): Organelle that forms a network of tubules. The RER is an extension of the nuclear envelop. It appears grainy because it is studded with ribosomes. This structure is involved in protein synthesis and export.

Smooth Endoplasmic Reticulum(SER): This structure is involved in lipid and steroid synthesis, metabolizes carbohydrates and steroids, regulates calcium concentration and is also involved in detoxification.

Receptors: are special proteins found on cell surface and they are used for communications. They interact with hormones from the endocrine glands and neurotransmitters from nerve cells.

Transport Through the cell

The word transport refers to how things are taken from one place and carry to another.

Diffusion:
is defined as the movement of molecules from an area of high concentration to an area of low concentration and it requires no energy.  In nature, molecules are always vibrating.  When vibrating molecules collide they move in opposite directions and spread apart.  Small molecules like water, oxygen and carbon dioxide can diffuse freely through the cell membrane. 

Osmosis:
is the diffusion of water through the cell membrane.

Active Transport:
Active transport occurs when molecules move from an area of low concentration to an area of high concentration through the cell membrane with the use of energy (ATP).  This type of transport requires the assistance of a transport protein.

ANIMATION of ACTIVE TRANSPORT

Both diffusion and active transport can be observed with the aid of an indicator.

Indicator:
An indicator is a chemical that changes color when it comes in contact with certain substances.

Starch Indicator:
When starch comes in contact with iodine, it turns black.  Therefore, iodine is a starch indicator.


Glucose indicator:
When Benedict's solution comes in contact with glucose and the solution is heated up, it turns creamish green or orange.  Therefore, Benedict's solution is a glucose indicator.

CLICK HERE TO QUIZ YOURSELF


INSIDE A CELL

CELLS ALIVE

CELL GAMES AND QUIZZES


CLICK HERE TO SEE ANIMATION OF RECEPTORS.


INTERACTIVE PARTS OF THE CELL




Enzymes:
are special proteins that make it easier for chemical reactions to occur inside an organism. How well an enzyme works depends on environmental factors such as pH and temperature.  Improper pH and improper temperature can denature the enzyme by changing its shape.

INTERACTIVE ENZYME1


ENVIRONMENTAL FACTORS ON ENZYME ACTIVITIES pH AND ENZYME FUNCTION

WHAT PROCESSES CONTROL THE FLOW OF MATERIALS IN AND OUT OF THE CELL?

• Diffusion is a process that allows materials to move in and out of the cell based on their concentration. Diffusion occurs when molecules move from an area of high concentration to an area of low concentration without using any energy. The molecules bounce against each other and spread. The molecules must be small enough to go through the holes in the cell membrane.

• Active transport is a process that allows molecules to move in and out of the cell from an area of low concentration to an area of high concentration.  It requires energy and the assistance of a transport protein.

To learn more, click this link. CELL ANIMATION VIDEO

Another cell animation CELL ANIMATION

• Compare plant cells to animal cells
• What is it that plant cells make, animal cells cannot make and they both use?

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