Plants

What are Plants? Plants are living organisms composed of one or more cells. A cell is the smallest unit that can be said to be alive. Some plants —such as some types of algae— are a single cell. (Similarly, some animals, like amoebas, are a single cell.)

Like animal cells, each plant cell has a nucleus (see the picture of a plant cell below). Having a cell nucleus is a key characteristic of all living things.

One difference between plant and animal cells is that the cells of plants have "walls", which are rigid and firm. Animal cells do not have cell walls but thinner cell membranes. This makes sense because plants do not have skeletons that support them. If plant cells did not have firm cell walls, plants would be more or less shapeless blobs.

In the cell shown below, you can put the cursor on the red triangles to see a description of the tiny organs ("organelles") and other substances inside the cell.

One important function of the DNA in the cell's (Select one) nucleus endoplasmic reticuli mitochondria chloroplasts is to make very important molecules called proteins. Proteins are made in cell organelles called ribosomes (not shown above). Proteins do most of the work in cells and are required for the structure, function, and regulation of the plant (or animal).

Photosynthesis, another important process in which sugars are made, happens in the (Select one) nucleus endoplasmic reticuli mitochondria chloroplasts in plant cells.

Plants usually grow in one location (rather than move around, like most animals do). Because of this, plants must depend on their local environment —and themselves— for nourishment. Plants get some nutrients they need through the absorption of water and minerals through their roots.

Plants make their own food (sugars) through the process of photosynthesis.  In this process, sunlight provides the energy to convert carbon dioxide and water into sugars. This process happens in the chloroplasts in the cells of plant leaves.

Plants can be divided into two main groups: Vascular and Non-vascular. (See the diagram below.)

• Vascular plants have cells that form tubes for carrying water and nutrients throughout the plant. Non-vascular plants do not have tubes to carry water and nutrients. Instead, water and nutrients move from cells to their neighboring cells. In case you were wondering, this is why (as shown in the picture of the plant cell two pages ago) the cell walls have little holes in them. This is so water and other nutrients can move from cell to cell.

Plant Hierarchy

Q1: Do you think that humans are more like vascular or nonvascular plants? Why?
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Humans are more like vascular plants because both humans and vasular plants have tubes that carry water and nutrients throughout their bodies. In humans, we call these arteries and veins.