Plants are amazing because they convert carbon dioxide into oxygen.
They only need sunlight and water to survive, unlike animals.
Everything we eat either comes from plants or from something that ate plants.
Plant Evolution
Plants likely evolved over 500 million years ago.
Earliest land-plant fossils date back over 400 million years ago.
These were lycophytes, which reproduce through spores.
Some lycophytes evolved into scale trees, forming coal forests during the Carboniferous Period.
Scale tree forests fossilized into coal.
Angiosperms (flowering plants) developed around 65 million years ago.
Cellular Structure: Eukaryotic vs. Prokaryotic Cells
Plant and animal cells are eukaryotic, meaning they have a "good kernel" (nucleus).
Eukaryotic cells are more advanced than prokaryotic cells.
Prokaryotic means "before the kernel" and includes bacteria and archaea.
Eukaryotic cells have a nucleus containing DNA and enclosed by a membrane.
Eukaryotic cells have organelles suspended in cytoplasm (mostly water).
Differences Between Plant and Animal Cells
Plants evolved from green algae.
Plant cells have a rigid cell wall made of cellulose and lignin.
Cellulose is the most common complex carbohydrate, a chain of glucose molecules.
Cellulose is hard to digest for animals.
Cell walls provide structure and protection to plants.
Lignin and cellulose make trees strong and resistant to deterioration.
Lignin and cellulose are roughage for humans; indigestible but useful for the digestive system.
Some animals (sloths, goats) have bacteria in their stomachs to digest cellulose into glucose.
Humans lack these bacteria and cannot digest cellulose effectively.
Cellulose and lignin burn, releasing energy.
Photosynthesis and Plastids
Plants make their own food through photosynthesis.
Plant cells have plastids, organelles for making and storing compounds.
Plastids and mitochondria originated as bacteria absorbed into plant cells.
Plastids and mitochondria have double membranes.
Chloroplasts are the most important plastids, converting light energy into sugar and oxygen.
Green parts of plants contain cells filled with chloroplasts.
Vacuoles
Plant cells have a large, central vacuole.
Vacuoles store water, providing turgor pressure to reinforce the cell wall which results in rigidity.
Vacuoles also store other compounds and wastes.
Animal cells have vacuoles, but they are smaller and don't provide structural support.
Basic Plant Cell Anatomy
Cell Wall: Rigid, made of cellulose and lignin. Provides structure. Cell wall <br/>eq cell membrane. It's on the outside of the cell membrane. Cell wall <br/>eq bone. Plant bone doesn't exist.
Nucleus: Contains genetic information and directs cell activities; found in a membrane bag.
Plastids: Including chloroplasts, which are food-making machines that use photosynthesis.
Central Vacuole: Stores water and other substances, providing structural support.
Impact and Appreciation
Plant cells stacked together form a plant.
Unique features of plant cells enable plants to provide food and air.
Appreciate plants for their hard work and service.