Topic 2 The World of Plants Standard Grade Biology
World of Plants is divided into: A- Introducing plants B- Growing plants (Pollination, Fertilisation, Asexual reproduction) C- Making food
The life cycle of a plant
There are 7 stages in the life cycle of a plant.
seed / fruit Formation seed dispersal germination flower formation pollination fertilisation development
Seed coat Forms a tough protective layer Food store Provides the embryo plant with food. Embryo shoot Embryo root Embryo – grows into plant
Using a scalpel, carefully dissect your seed in half lengthways.
Draw a diagram of what you can see.
Identify the parts,
and label your drawing
This is an Exam Board Investigation that makes up part of your Practical Abilities grade (20% of finals)
Planning may be done in small groups but after this you must work on your own
Write in your Investigation booklet.
What affects germination?
3Bio2 Brainstorm 16/03/07
Spacing / number of seeds
Humidity / water volume
Type of seeds
Size of seeds
Type of soil / mass
Depth of planting
Gases / oxygen levels
Measure by % germination after set time
Germination and Temperature
Example of results table. Also draw a graph.
What conclusions can you draw from your experiment?
How could you have improved it?
Temperature o C No. of seeds No. of seeds germinated Percentage germination 4 25 20 25 50 25
Seeds need certain conditions to germinate:
to activate enzymes which digest stored food
Needed for the production of energy for germination
Needed for the enzymes to work effectively.
Germination is the development of a new plant from the embryo in a seed.
Germination and Temperature
The best temperature for germination of a species of plant is known as the optimum temperature .
The optimum temperature is normally between 15 o C and 30 o C.
Structure of a Flower
Petal Stigma Anther
Petals Stigma Anther Filament Ovary Sepals Ovules Nectaries Style Collect a cut-out flower, colour it in and put it together. Carpel female parts Stamen male parts
What do the parts do? Sepals- protect the flower when it is a bud Petals- colourful to attract the insects Nectaries- give out sugary liquid to attract insects Stamen - anther produces male sex cells (pollen) Carpel- stigma traps pollen Style is where pollen tube grows down to female sex cells. Carpel- ovary produces female sex cells (ovules)
Why is the seed coat important?
Name the parts of the embryo plant.
Why is the food store in a seed important?
Name the three factors required for germination.
Where are a plant’s sex organs found?
Name two parts of a flower that attract insects.
Name the male part of a flower.
Which part of the flower contains ovules?
Which part of the flower produces pollen?
Which part of a flower catches pollen grains?
Pollination involves the transfer of pollen (male gamete ) from the anther to the stigma (outermost female part)
If it is in the same flower it is called
If between different flowers it is called
Plants are pollinated by insects or the wind .
Insect Pollinated Plants
Wind Pollinated Plants
Look at the Botanics Posters
Which features are from wind pollinated or insect pollinated plants?
Construct a table to show the differences between insect and wind pollinated plants.
Fertilisation involves the fusion of the nucleus of the male gamete (in the pollen) with the nucleus of the female gamete (in the ovules).
The pollen grain grows a tube.
The tube reaches an ovule.
The gamete nuclei fuse (fertilisation) and a zygote (seed) forms.
Pollen tube growth
Fertilisation Once fertilisation has taken place the zygote (fertilised ovule )becomes a seed , and the ovary becomes a fruit . The petals die and fall off. The plant seeds are in the fruit .
What are fruits like?
The fruits can be:
- soft & fleshy
- hard & dry
What fruits can you think of?
What are their seeds like?
Draw a table with headings for each type and write some examples for them.
Types of Fruits Soft & fleshy Hard & dry Apple Tomato Hazelnut
Seed Dispersal- why?
Seeds must be carried away (dispersed / scattered) from the parent plant to:
Reduce competition for:
Seed Dispersal Dispersal method Description Seeds/ Fruits Wind Seeds are designed to travel as far as possible. May have extensions which act as parachutes or wings. Fruits may be shaken like a pepper pot.
Seed Dispersal Dispersal method Description Seeds/ Fruits Animal (internal) Fruit is brightly coloured to attract animals. When eaten the seed travels with the animal, survives acidic digestive juices and is passed out in the faeces.
Seed Dispersal Dispersal method Description Seeds/ Fruits Animal (external) Some have little hooks or sticky substances so they stick onto the animal’s fur, are carried away and rubbed off later. Some carried away by animals and dropped.
Cut out the seeds, match and stick them into appropriate columns in a table, for:
[There is also mechanical (eg broom, sea cucumber) and water (eg coconut) but you don’t need to know them for Standard grade]
Listening exercise on seed dispersal
Listen to the tape,
Use the commentary to help you answer questions on your handout.
World of Plants Workbook p41 Comparing Lime and Sycamore seeds. Go through the problem solving activity
What term is used to describe male and female gametes?
What is pollination?
Name the two types of pollination.
Describe the differences in the pollen between insect and wind pollinated plants.
Explain why the stigmas of wind pollinated flowers hang outside the flowers.
Why do wind pollinated flowers not produce nectar?
How does the male gamete reach the female gamete?
What is a fruit?
Name three ways in which fruits and seeds are dispersed.
Why is it important that fruits and seeds are carried away from the parent plant?
Types of reproduction Sexual reproduction Involves 2 parents and sex cells ie. pollen and ovule join to make a new individual.
Involves 1 parent and no sex cells.
Ways they naturally reproduce include:
- ( Bulbs )
Tubers Tubers are underground food stores which stores food over the winter and provides a new plant with food until it can make its own. Food made by the new plant is sent to make new tubers. Thereby reproducing itself. Examples: potato, artichoke, yam, cassava, water chestnut, arrowroot Taro- Japanese potato
Arrowroot arrowroot = arrow root = Chinese potato (this name also is used for jicama ) = goo = seegoo = arrowhead = Chinese arrowhead = tse goo = ci gu = tsu goo Notes: The name arrowroot is more commonly associated with a thickener that's made from the plant. A fresh arrowroot tuber looks like a small onion, only without the layers. It should be peeled, and then it can be boiled or stir-fried. Look for it in Chinese markets during the winter.
Cassava cassava = casava = manioc = mandioca = tapioca root = yucca = yucca root = yuca root = Brazilian arrowroot Pronunciation: kuh-SAH-vuh Notes: People in Hispanic countries use cassavas much like Americans use potatoes. There's both a sweet and a bitter variety of cassava. The sweet one can be eaten raw, but the bitter one requires cooking to destroy the harmful prussic acid it contains.
Topinambour tapioca root Notes: Water chestnuts are delightfully sweet and crisp- if you buy them fresh. You need to peel off their brown jackets and simmer them for five minutes before stir-frying. Tinned Water chestnuts are easily available but not nearly as good. If you use them, blanch them first in boiling water for thirty seconds. Topinambour Water chestnut Chinese water chestnut
Bulbs Bulbs are also underground food stores which work in the same way as tubers. The difference is that bulbs have thick fleshy ‘leaves’. Keukenhof gardens near Amsterdam Holland.
3. Dec. - Jan. Cooling Period Rest period. In order for bulbs to bloom in the spring they need weeks of at least 5 o C. Frost at this time doesn’t harm them. 1. Sept.- Oct. Planting Time The tulip bulbs are going to be planted twice as deep as the bulb is high. They have no roots at this stage. 2. November Making Roots The roots start growing out of the base, establish themselves taking nutrients from the soil. Mother bulbs get ready for winter. 4. Feb. – March G rowing Period The bulbs begin to change as the starch, or carbohydrates in them turns to sugar. As this occurs, the leaves and flower gradually push up-wards out of the bulb. 5. April – May B looming Time The tulips are in bloom-they receive their nourishment from the roots-only the brown skin of the bulb remains as all of the energy has gone to the bloom. 6. May – June Regeneration After flowering the blooms are cut and the leaves are left on the plant. The new daughter-bulbs use the food in the leaves to grow. 7. July - Sept. Multiplying Up to five small bulbs can be expected to grow out of the mother bulb. They form their roots slowly, and develop their blooms and leaves within the bulb, for next year's plant.
Runners Runners are side shoots which grow out from the parent plant. Buds form at points along the runner and eventually these buds form roots and grow into new plants. Examples: spider plant ( Anthericum ), strawberry ( Fragaria x ananassa)
Flame violet ( Episcia reptans ) Collect Information Card “ Asexual Reproduction” Take short notes from it.
World of plants workbook
“ Advantages of asexual reproduction”
Read p32 & 33.
Copy and complete the table.
Summarising advantages & disadvantages of sexual versus asexual reproduction
Reproduction- advantages Asexual Sexual Genetically identical offspring (clones) which have parent’s strong characteristics (but weak ones also passed on) and are suited to their environment. Narrow distribution spreading over the area quickly as no vulnerable stages involved. Genetically different offspring- variation . More chance of survival if conditions change. Wide distribution Reduces competition for water/light/nutrients as no dense growth around the parent. Using seeds allows the offspring to travel to new areas.
A clone is the name given to the genetically identical plants produced from a single parent plant.
They are formed during asexual reproduction only.
Artificial Propagation People can make use of plants’ ability to reproduce asexually (instead of using seeds) by using methods of artificial propagation such as: - Cuttings - Graftings Again this produces genetically identical offspring (clones).
Cuttings They can be placed in moist soil or water (and sometimes dipped in rooting powder). Cuttings are small pieces of stem with some leaves attached, the new plant grows from this.
Grafting A cut stem of one plant (with good flower or fruit growth) (the graft) is taken and firmly attached to the rootstock of another plant (which has a strong, established root system) (the stock) . Examples- roses, fruit trees
Grafting- advantages Allows you to clone the commercial qualities of a particular fruit variety on another tree. Seed trees have highly variable fruit quality. They come into production much earlier (2-3 years) than trees grown from seed (5-10 years).
Activity World of Plants Workbook p42 The effect of rooting powder on cuttings Collect some graph paper and work through the problem solving activity
Activity World of plants workbook p33 “ Artificial propagation- commercial advantages” Read page. Collect Information sheet Write short notes on it.
Commercial aspects Artificial propagation has allowed us to adapt and improve plants for our own use. Some of the benefits include:
Quick production of large numbers of genetically identical plants.
Specific varieties, desired features or consistent quality can be produced especially in fruit, flowers.
How many parents are involved in asexual reproduction?
Name 3 ways in which plants reproduce asexually.
Give 2 examples of plants that reproduce asexually by producing runners.
What term is used to describe a population of genetically identical plants?
Name 2 common methods of artificial propagation.
Give the commercial advantages of artificial propagation.
One Runners, tubers, bulbs Spider plant, strawberry Clones Cuttings, grafting Quick method, producing large numbers of plants, of known quality and specific variety
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