Week 9 - Introduction, Moving Water, Life Cycles, Structural Adaptations, and Plant Needs

Exercise 1.3


Lesson 1.3 Reproduction of Seed Plants
 
 
ACTIVITY A: Life Cycles

 



Required Readings

Science in Action 7
pages 109 to 115
or

Science Focus 7
pages 120 and 125

 


In this lesson you will examine the life cycle of seed plants. Understanding the life cycles of seed plants allows use to grow the food we need to feed the world. You and your family have a garden that allows you to enjoy the flavour and health benefits of fresh vegetables. I hope you enjoy this lesson and can put the information you learn into practice in a small garden of your own. Watching your garden grow can be an amazingl experience.

Life Cycles - What Are They?

A life cycle includes the stages that a living organism goes through from one generation to another. Most organisms go through a life cycle. Humans, like you and I, have a life cycle, and so do seed plants. Let's examine our own first.

The human life cycle begins when a sperm (from the father) and an egg (from the mother) join to form a new human life. The baby grows inside its mother and is then born into this world. The baby grows to a child and then to an adult. Adults reproduce and produce another generation of people. That's the life cycle of a human. Lets now go on and examine the life cycle of a seed plant.

Life Cycle of Seed Plants

If you live in a farming area you are already quite familiar with the life cycle of seed plants. First, a seed in put into the ground. There it germinates and begins to grow out of the ground. Over the growing season the plant grow stronger and taller until it is ready to reproduce. Now the plant grows a flower. The flower is fertilized, possibly by insects such as bees, or perhaps by the wind. The attractive parts of the flower, like the petals or the parts that produce an attractive scent, have now done their job, and begin to die back. The plant now puts most of its energy into producing the seeds. As the seeds mature, they drop from the plant, or are blown away on the wind to begin a new generation of plants when favourable conditions for life return again.




So lets quickly review that again in point form: 1. The seed germinates and grows to a tiny seedling.
2. The seedling grow to an adult plant which contains flowers.
3. The flowers are pollinated and new seeds begin to grow and mature.

 

Sexual Reproduction in Plants

Seed plants use flowers to sexually reproduce. This means that each flower contains both the male and female reproductive organs.

Sexual reproduction uses up great deal of energy in plants so there must be some real advantage of sexual reproduction over asexual reproduction. In sexual reproduction, the offspring are different from either of their parents. This variation may allow the new plants that grow to survive conditions or disease that their parent plant can't. This advantage is found in all species that reproduce sexually even us! For example, you are a totally unique person. No one else is exactly like you (unless you have a twin).

Activity: Examining the Parts of a Flower

Use your textbook and the Internet to name the flower parts in the diagram below. You will be recording this work in the lab that follows. You could try this document for flower part information: Flower Parts

 



Pollination

Pollination is the act of transferring the pollen grains from the stamen to the pistil. Some plants can self-pollinate. In this case the pollen transfers from the stamen to the pistil on the same flower. Many grains like wheat and barley are self-pollinators.

Other plants are cross-pollinated.

This means that the pollen from on flower is transferred to other flowers by wind or animal activity. Our friend the bee is one of the main pollinators of our food crops. Other animals like humming birds, bats and other insects look after the job. In return for their efforts, they are rewarded with nectar that many eat on the spot. There are many professional beekeepers in Alberta who travel with their bees to ensure that crops get fertilized.

Moving On

Other seeds are hidden with fruits such as apples, mangos and kiwi fruit. Why do you think the plant goes to so much trouble and energy to make fruit? Plants need to ensure that the seeds they produce will disperse (spread out) over a larger area. One way to ensure this is to have an animal eat the fruit and then walk or fly away from the plant. When the animal goes 'to the bathroom' (they don't really have bathrooms - but you know what I mean) the seeds are deposited on the ground with a fresh supply of fertilizer. This usually happens a long way away from the parent tree and so the plants can eventually spread out over a large area. Other plants drift on the wind like the dandelion or have barbs on them to catch on an animals fur or our pants. However they do it, they must spread out away from the parent plant. Tumbleweeds have a neat way to do it. The parent plant breaks away from the ground and as it blows around in the wind, the seeds fall off.

Seeds

 
 

Exercise 1.3 - Flower Labelling

 

 
   
   

 
ACTIVITY B: Vegetative Reproduction

 



Required Readings

Science in Action 7
pages 114 - 115
or

Science Focus 7
pages 118 - 119

Plants can reproduce in two totally different ways. Selective breeders primarily make use of sexual reproduction in plants to slowly change the characteristics of plant. On the other hand, once you have the plant varieties that you wish to use, asexual reproduction can be helpful in maintaining the characteristic which are required. In asexual, or vegetative reproduction the "parent" plant grows new plants from its roots, stems, or leaves.

When plants reproduce asexually, the offspring will have the identical characteristics of their parent. Many trees spread by producing new seedings from their roots. A Poplar, or Trembling Aspen forest can be created from very few parent trees.

Some plants such as strawberries will send out runners to implant in the soil and produce another identical plant. Runners are similar to roots but the move out from the plant above ground.

Man has also found ways to make use of vegetative reproduction through layering, grafting and cutting.

In layering, a branch of a parent plant is bent and pointed back into the soil where it is partially covered. Roots will grow from the buried stem and a new plant with the same characteristics of the old one will form. Eventually the new plant can be cut away and replanted. This is a common technique for blackberry, raspberry, and rose bushes.

Grafting is another use of vegetable reproduction. A shoot or branch from one tree in inserted (grafted) into a fresh cut in another tree. A seal or bandaid is applied to keep out infection and the second plant will grow and become part of the first. This is a common practice with apple trees. As trees take so long to grow this is a way of placing apple branches that will produce hardy fruit on trunks with hardier roots and several years head start in growth. There are trees growing in apple orchard that have numerous varieties of apple grafted onto the same trunk.

Plant growers commercial and residential alike make common use of cutting as a way to make a duplicate of a plant and its characteristics. This method will produce offspring much faster than from seed. They only question that remains is how much of a plant must be cut to make the best types of cuttings.

 
 

     
       
       

     
    ACTIVITY C: Cutting Investigation (This Activity is Optional)
    What are the best type of cuttings to take? Find out in this investigation!

    PROBLEM

    How well will plant cuttings with one leaf, two leaves, three leaves, and no leaves grow? Note: improvise if you need to ie. cut down the number of cuttings by one, find a partner or two and use the same cuttings to gather data from, etc.

    HYPOTHESIS

    Form a hypothesis about what you expect to happen at the bottom of each of the plant stems after one week.

    MATERIALS

    Scissors or utility knife
    Ruler
    Four clear plastic glasses
    Aluminium Foil
    Water
    Plant, such as a coleus, begonia, or impatiens

    PROCEDURES

    1. Set out your four cups. Label each cup with the number of leaves which the sample will have. Fill the cup with water and cover the top of the cup with a layer of aluminium foil. Tape the aluminium foil around the edge of the cup to get a more rigid seal.
    2. With a pencil, punch a small hole in the centre of the aluminium foil.
    3. Use the scissors to take four small clipping (approximately 5-7 cm long) from your parent plant. Make sure all the clipping come from the same plant. Take one cutting with no leaves, one with one leaf, one with two leaves, and one with three leaves.
    4. Insert the cut end of the cutting through the hole in the foil, ensure that the bottom of the cutting dips completely into the water.
    5. Place your cuttings in adequate sunlight.
    6. Make drawn observations everyday for one week of the bottom of the stem. Make sure to record the date in your table when you first see roots. Draw what you see on each plant for one week. Use a ruler to measure the length of the roots if necessary.
     
     

     
     
     

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