Biology - Mr. Willets
Seeds / Fruit
Angiosperms are the flowering plants. They have flowers which produce pollen (sperm) and egg cells.
Once the sperm fertilizes the egg, the zygote grows into a plant embryo and becomes part of the seed. The seed(s) are then covered by the fruit. The name angiosperm actually means covered seed.
Seeds are a very important evolutionary advance. They allow the plant embryo to remain dormant and protected until conditions are right. At that point, the embryo can start to grow using the stored food until its own leaves start photosynthesizing.
Seeds have three main parts- the embryonic plant, the stored food and the seed coat. Some angiosperms have seeds with two cotyledons. These are called dicots. Other have seeds with only one cotyledon. These are called monocots. The cotyledons are basically where the food is stored. (not exactly true but close enough)
Most monocot plants are tall and thin. They include grasses, grains (like wheat, oats, barley, corn) and many familiar flowers (daffodils, irises, lilies, tulips et al.).
The two cotyledons in a dicot seed can easily be separated once the seed coat is removed. You may have done this playing with peas or lima beans when you didn't want to eat them.
The embryonic plant inside the dicot seed has 3 main parts- a root, a stem and 2 leaves. These, of course, all have fancy names which we will ignore.
Monocot seeds cannot be separated into two parts (for obvious reasons). An example is a kernel of corn.
Seeds do not germinate (start to grow) unless exposed to the right conditions. Seeds produced in the fall (like apple seeds) must be exposed to freezing temperatures for several weeks before they can germinate.
This assures they start to grow in the spring and not in the fall (and be shortly killed when winter arrives)
Most seeds need adequate water to soften the seed coat so the embryo can grow from it. A suitable temperature is also required. Some seeds require sunlight to start to grow. This assures that they are not buried too deeply in the soil where they would not be able to grow to the surface.
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Seeds are located inside fruits. The biological definition of a fruit is anything that contains seeds. The fruit can protect the seed but mostly it is used to help disperse (spread out) seeds.
The type of fruit that you know surround the seeds with a fleshy sweet material. This attracts animals which carry the seeds away as they eat the fruit. Even if they eat the seeds, the seed coat will protect the seed and it will pass through the animal unharmed. When put into the environment, it will be surrounded by fertilizer. Sometimes there is only one seed that is so big that it likely won't be eaten. We call these pits.
Many fruits are made to carry the seeds in the wind. The maple tree "helicopters" are fruits designed to do this. You probably have removed the seed from this fruit many times. The official name for these are maple tree samaras. The fuzzy white things on a dandelion are fruits. Each carries a seed.
The coconut is a fruit that floats. Burrs are fruits that stick to animals (and your socks). Some fruits actually throw the seeds away from the plant. The tropical sandbox tree has fruit that can toss seeds over 300 feet away.
"Seedless" fruits have been produced by artificial selection. In these cases, the seeds are so small that they are not noticed and can be eaten easily.
Biology- Mr. Willets
Questions
1) What does the name angiosperm actually mean? ________________________________
What covers the seed? ________________
2) Seeds protect the embryonic plant so it can remain _________________ until conditions are suitable.
3) What word describes when a seed starts to grow? __________________________
4) What are the three main parts of a seed? a) _________________________
b) ___________________________ c) __________________________
5) A dicot plant has seeds with 2 __________________________. These basically store ___________
What do we call plants whose seeds have only one of these? ________________
6) Give some examples of monocots- ______________________________________________ Most of these are recognizable because they are ____________and _____________
7) What tells you that a lima bean plant is a dicot? _______________________________________
8) The embryonic plant in the seed has what three main parts? __________________ , _____________
and ______________________
9) Apples grow in the fall. If the seeds germinated immediately, what would happen to the young tree?
____________________________________________. Apple seeds do not germinate until after what has happened? __________________________________________________________________
10) Water is needed for germination to ______________ the seed coat.
11) If you were asked as a food shopper to define what a fruit is you would probably say that it had to be ________________________________________. As a biologist you would say that it is anything
that _____________________________________ What foods that you eat are biologically fruits although you don't think of them that way? __________________________________
12) The main purpose of the fruit is to _____________________ the seeds.
13) Fleshy, sweet fruits attract ____________________ which carry the seeds away.
14) Maple tree fruits use the ______________ to carry the seeds away. (some of you may know this- what can you do with the maple fruit after removing the seed from it?_______________________________)
15) If you break open a burr- what will be inside? ______________ Therefore, it is a ___________.
How does it help disperse (spread out) seeds? __________________________________________
16) Why is the term "seedless fruits" an oxymoron? (look up oxymoron if you don't know what it is)
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17) Are seedless fruits actually seedless? ______ Explain ___________________________________