CHAPTER 1
Cell Theory
Over time scientists came have been able to use technological developments
to assist in the creation of what we call today Cell Theory.
1. All living organisms are composed of one or more cells.
2. Cells are the basic units of structure and function in all organisms.
3. All cells come from previously existing cells.
4. The activity of an entire organism depends on the total activity of its
independent cells.
A typical cell has numerous membrane-bound ORGANELLES, specialized
structures that perform specific functions in the cell.
ANIMAL CELL
PLANT CELL
YOU NEED TO KNOW THE FOLLOWING DEFINITIONS:
Nucleus
Nuclear Membrane
DNA – Deoxyribonucleic Acid
Chromatin
Nucleolus
Ribosome
Cell Membrane
Cytoplasm
Endoplasmic Reticulum
Mitochondria
Golgi Bodies
Vacuoles
Lysosomes
Animal and Plant Cells
Animal and plant cells have many similarities. They do however have a few
differences.
 Plant cells have a fibrous cell wall that provides structure and
support for the cell. Plants need this cell wall to provide with
support. Example and sunflower.
 Plant cells contain chloroplasts. They are organelles that
enable the plant to make their own food through the process of
photosynthesis.
 What are the similarities between plant and animal cells?
The Process that ensures each new cell has a nucleus with a complete set on
instructions (DNA) is called MITOSIS.
MITOSIS
Before mitosis can begin, the nucleus must make a copy, or replica of its
chromatin, so that there are two complete sets of DNA. This is known as
replication. The replicated chromatin coils up to form double-stranded
chromosomes. The end result of mitosis is the separation of replicated DNA
into two complete sets of DNA, one for each new cell’s nucleus.
Prophase – The nucleolus and the nuclear membrane disappear. Spindle
fibers form and stretch across the cell from centrioles that have moved to
opposite ends of the cell. The spindle fibers attach to one side of each
centromere.
Metaphase – The tugging action of the spindle fibers pulls the doublestranded chromosomes into a line across the middle of the cell
Anaphase – The spindle fibers begin to contract and shorten which pulls the
centromere apart. One of each of the replicated strands to moves to opposite
ends (pole) of the cell.
Telophase – The spindle fibers begin to disappear. And a nuclear membrane
forms around each set of chromosomes. A nucleolus appears within each
new nucleus. The single stranded chromosomes start to uncoil into thin
strands of chromatin.
NOW THERE ARE TWO NUCLEI IN ONE CELL
In animal cells, the cell membrane pinches in near the middle of the cell,
dividing the cytoplasm into two new cells.
In plant cells, a cell plate develops across the center of the cell, forming a
new cell wall between the two new cells
Interphase – During Interphase the cell grows, replicates its DNA, and
becomes prepared for the first phase of mitosis
AS A RESULT OF MITOSIS, THE NUMBER OF CHROMOSOMES
IN THE NUCLEUS OF EACH CELL IS IDENTICAL TO EACH
OTHER AND TO THE NUMBER IN THE ORIGINAL CELL
CANCER
-is the direct result of cells dividing uncontrollably
-the continue dividing and pile up on top of one another, forming a tumor or
lump
-these excess cells can stay contained in one area or, move to other parts of
the organism
-the gobble up oxygen and nutrients for themselves, crowding out other cells
and robbing them of their food
Asexual Reproduction
Mitosis and cell division are not only important to human growth and tissue
repair, but are also important in asexual reproduction.
Asexual Reproduction is the formation of a new individual that has identical
genetic information to its parent
BACTERIA
 Are unicellular organisms that do not contain a true nucleus
 Reproduce asexually through a process known as binary fission
 In binary fission a parent cell divides so that each new cell contains a
single chromosome carrying a complete set of DNA identical to that
of the parent
PROTISTS
 Are unicellular organisms that do contain a true nucleus
 Mitotic cell division results in the formation of two identical offspring
 Protists are important because they form the basis of many food
chains and are responsible for many diseases that affect humans.
FUNGI
 Fungi are composed of many filaments called hyphae which grow
over the surface of and into the bodies of other organisms to obtain
food
 Can reproduce asexually three ways, fragmentation, budding and
spores.
 In fragmentation, a small piece or fragment, breaks away from the
main mass and grows into a new individual.
 In budding a copy of the nucleus is made, then a tiny bud begins to
form on the cell wall. This bud, containing the new nucleus continues
to grow and eventually breaks away.
 A spore is a reproductive cell that can grow into a new individual
through mitotic cell division. When mature, spores can float about on
air currents.
ANIMALS
 Animals can be divided into two main groups, vertebrates (those with
backbones) and invertebrates (those without backbones)
 Many invertebrates can reproduce asexually to form one or more
identical offspring from a single parent
PLANTS
 Unlike many animals, plants continue to grow throughout their lives.
 The tips of their roots and stems contain growing areas called
meristem.
 Meristem is made up of unspecialized cells that undergo mitosis and
cell division repeatedly, producing new cells.
CHAPTER 2
Sexual Reproduction
Your body has specialized organs (GONADS – testes and ovaries), that
make specialized cells (GAMETES – sperm and eggs), for sexual
reproduction. The gametes from two parents combine during a process
called fertilization to form a new cell or ZYGOTE. This zygote is the first
body cell of a new organism.
The total number of chromosomes in a human body cell is 46 – this is
referred to as diploid. These 46 chromosomes can be arranged into 23 pairs
of chromosomes that resemble each other in size and shape. These matching
pairs of chromosomes are known as homologous pairs. You receive one
pair from your mother and on from your father.
Human gametes (sperm and eggs) have 23 chromosomes and are called
haploid. Only haploid gametes can combine during fertilization to form a
diploid zygote. Mitosis ensures that the chromosome number does not
change, while the process that ensures each gamete contains only one-half
set of chromosomes is called MEIOSIS. Meiosis ensure that each gamete
has a different combination of the chromosomes that were present before
meiosis.
Despite the differences among animals, the fundamental sequence that
allows them to reproduce sexually is the same:
 Meiosis produces gametes
 A male gamete combine with a female gamete
 A zygote is produced and develops into an embryo
 The embryo develops through mitosis and cell division into mature
offspring
For sexual reproduction to be successful, the following two requirements
must be met:
 Both male and female gametes must arrive at the same place and time
for fertilization
 The zygote must receive adequate food, moisture, warmth, and
protection to develop
EXTERNAL FERTILIZATION
 The sperm and the egg meet outside the bodies of both parents
INTERNAL FERTILIZATION
 The sperm and the egg meet inside the body of the female. The sperm
travel from the male’s body into the female’s body to meet the egg.
HEMAPHRODITES
 Individuals that have both female and male reproductive organs