Looking at Cell Functions
All cells have a purpose. If they don't do anything productive,
they are not needed anymore. In the big picture, a
cell's purpose is much more important than acting as small
organizational pieces. They had their purpose long before they
started working together in groups and building more
advanced organisms. When alone, a cell's main purpose is to
survive.
Even if you were a single cell, you would have a purpose. You
would have to survive. You would be moving around (probably
in a liquid) and just trying to stay alive. You would have all of
your pieces inside of you. If you were missing a piece you needed to survive, you would die.
Scientists call those pieces organelles. Organelles are groups of complex molecules that help a
cell survive.
All Cells are not Created Equal
In the same way that cells survive in different ways; all
cells have different types and amounts of organelles. The
larger a cell becomes the more organelles it will need. It
makes sense if you think about it. If you are a big cell, you
will need to eat more than a little cell. You will also need to
convert that food into energy. A larger cell would need to
eat more and may wind up having more mitochondria to
process that food into energy.
While they might have a purpose, more advanced cells
have a difficult time surviving on their own. A cell from
your brain could not survive in a Petri dish for long. It
doesn't have the right pieces to live on its own. It does have the ability to transmit electrical
systems around your body. An amoeba could survive in a dish forever, thrive, and reproduce. On
the other hand, that amoeba will never help you transmit electrical impulses. The brain cell is far
more advanced and has specific abilities and organelles. Simpler cells have a better chance of
surviving on their own while complex cells can accomplish tasks that are more advanced.
Questions:
1. What do all cells have in common?
2. Can you think of a good analogy that describes the function of all cells? For example, in
class we discussed how cells are like factories, because each part of the cell has a job, and
they all work together to help the cell survive.
Flower Anatomy
The Flower:
The flower is the reproductive unit of some plants (angiosperms). Parts of the flower include petals, sepals,
one or more carpels (the female reproductive organs), and stamens (the male reproductive organs).
The Female Reproductive Organs:
The pistil is the collective term for the carpel(s). Each carpel includes an ovary (where the ovules are
produced; ovules are the female reproductive cells, the eggs), a style (a tube on top of the ovary), and
a stigma (which receives the pollen during fertilization).
The Male Reproductive Organs:
Stamens are the male reproductive parts of flowers. A stamen consists of an anther (which produces pollen)
and a filament. The pollen consists of the male reproductive cells; they fertilize ovules.
Fertilization:
Pollen must fertilize an ovule to produce a viable seed. This process is called pollination, and is often aided
by animals like bees, which fly from flower to flower collecting sweet nectar. As they visit flowers, they
spread pollen around, depositing it on some stigmas. After a male's pollen grains have landed on the stigma
during fertilization, pollen tubes develop within the style, burrowing down to the ovary, where the sperm
fertilizes an ovum (an egg cell), in the ovule. After fertilization, the ovule develops into a seed in the ovary.
Types of Flowers:
Some flowers (called perfect flowers) have both male and female reproductive organs; some flowers
(called imperfect flowers) have only male reproductive organs or only female reproductive organs. Some
plants have both male and female flowers, while other have males on one plant and females on
another. Complete flowers have stamens, a pistil, petals, and sepals. Incomplete flowers lack one of these
parts.
Task: Read the definitions then label and color the diagram below. When you are done, go find a flower in
the gardens, sit next and see if you can identify any of the parts below. Then, sketch, label and color the
flower you are observing in the box at the bottom of this page.
Definitions
anther - the anther is the tip of a flower's stamen
(the male reproductive organs of the plant) - it
contains the pollen.
filament - the filament is the part of the flower that
holds the anther (and part of the stamen, the male
reproductive organs of the plant)
ovary - the ovary is a female reproductive organ in
plants that produces ovules. It is at the base of the
pistil.
petal - a petal is one of the leafy structures that
comprise a flower. Petals are often brightly-colored
and have many different shapes.
sepal - the sepals are small leaves located directly under a flower - they are
the outermost part of a flower.
stem (also called the peduncle) - the stem supports the plant.
stigma - the stigma is uppermost part of the pistil, the female reproductive
tissue of a flower. The stigma receives the male pollen grains during
fertilization, when they travel through the style to the ovary.
style - the style is part of the pistil, the female reproductive tissue of a
flower. The style is a long tube on top of the ovary, and below the stigma.
Sketch, label and color a flower from the garden: