Life Science

Homework for Class 6 (after Fall Break)

Great work on the Tree Project!

Homework: During the break, complete the homework sheet I handed out in class (worksheet 1). Refer to your notes, my notes on this website below, and the handouts I gave you in order to fill out the homework sheet. This type of exercise will make up the bulk of your grade for the semester, so be sure to complete the homework sheet before next class.

Lecture: Types of Plants (continued), Flower Anatomy, and Photosynthesis

Types of Plants: Monocots and Dicots

Today we finally talked about seed-bearing plants. There are two types of seed-bearing plants: monocots and dicots. The main difference between them is how many "seed leaves" (called cotyledons) there are in a seed.

Memorize: Cotyledons are leaves in seeds.

"Mono" means "one" and "di" means "two," so a "mono"-cot has "one-cotyledon," whereas a "di"-cot has two cotyledons. Corn, for example, has only 1 cotyledon in each seed, so it is a monocot, while petunias have 2 cotyledons in their seeds so they are dicots. These cotyledons are absolutely essential while the plant is very young because they are the only way for the plant to make food before it grows true leaves.

Monocots are mostly grasses like common yard grass, prairie grass, wheat, and corn. Some flowers like iris are also monocots.

Dicots are all the remaining flowering plants like roses, violets, maple trees, ash trees, etc. There are a LOT of dicots.

Monocots and dicots have a few different characteristics. All monocots have parallel veins in their leaves, while dicots have branching veins. All monocots have flowers with petals in multiples of 3, while dicots have petals in multiples of 4 or 5.

Flower Anatomy and Seed Development

The center of a flower is called the ovary, which contains eggs. The carpel (also called the pistil) is a tube that sticks up out of the ovary. Thin tubes stick up around this called stamens, which hold pollen on their tops. Surrounding these are the petals. When a bee collects nectar and pollen from one flower, static electricity pulls pollen onto his hair, which he carries to other flowers. He cleans the pollen off himself, dropping it onto the sticky head of the carpel. The pollen grow tubes through the carpel until they meet the eggs in the ovary, thereby forming seeds. After this, the flower's job is done and it turns into a fruit.

Because apples don't fall too far from the tree, the sapling apple trees will have a tough time getting enough sunlight and water if they try to grow directly under their parent tree. This is why plants grow nutritious and delicious fleshy stuff around their seeds (the tasty part of an apple) so that horses and other animals will eat their apples, then deposit the seeds far from the tree when they are done digesting the apple. These seeds have an added benefit because they can grow in great fertilizer.

Photosynthesis

A plant's root system carries water (H2O) from the roots up to the leaves. Tiny holes on the bottom of leaves called stomata absorb carbon dioxide (CO2). Special cells on the top of leaves absorb energy in the form of sunlight. When they combine this energy, water, and carbon dioxide, they get two things: glucose (which is a sugar) and oxygen gas (which is what we need to breathe). Glucose is the plant's food, so this whole process is how a plant gets food.

Homework for Class 5

Complete the Tree Project. It is due in class next week. Bring your folder (blue or red) with all five worksheets, leaf and bark rubbings or presses, and tree sketches.

Lecture

Today we reviewed bacteria and their organelles, then discussed the simplest forms of plant life. Plants can be divided into those with seeds and those without seeds. Those without seeds can be divided based on whether they have distinct leaves, roots, and stems.

Algae, for example, have no distinct leaves, roots, or stems. Each cell needs to collect its own water, produce food, reproduce, etc. Each cell could hypothetically live on its own, so this kind of plant is like a collection of individual cells.

Mosses are an in-between case. They have some distinct leaves, roots, and stems, but not so much as other plants. They cannot grow very tall because they do not have a vascular system, which is a system that carries water throughout the plant (like a root system in more complex plants or the blood vessels in animals). Algae and mosses are both nonvascular plants. Since each cell needs to collect its own water, each cell needs to grow where the water is.

Ferns are an example of vascular plants. They have distinct leaves, roots, and stems. They produce spores instead of seeds, which makes them simpler than seed-bearing plants.

Homework for Class 3

Homework: Complete 1 worksheet for the Tree Project (handed out in class and attached below). Note: The student should not do more than 1 tree before next class so that I can correct any errors before they do all five. If the student is not able to complete it due to extraneous circumstances, please email me before our next class.

In class, we covered everything the students will need in order to finish the Tree Project.

1. How to estimate the size of a leaf using graph paper. 5 sheets of graph paper were provided.

2. How to estimate the circumference of a tree by wrapping a cord around it then laying the cord flat and measuring it with a measuring tape. (You can also use a fabric measuring tape if you have one.)

3. How to estimate the canopy of a tree (instructions attached below). 5 more sheets of graph paper were provided.

4. How to estimate the height of a tree. Hold a stick that is the same length as your arm. Hold your arm straight out, with the stick pointing straight up. Walk away from the tree until the tip of the stick lines up with the very top of the tree. Then measure the distance from the tree trunk to where you are standing. This distance will roughly equal the height of the tree.