Describe the various ways by which seeds are dispersed.
Seed dispersal takes place by various agent that is responsible for cross pollination; and this means to scatter seeds over a large area. The seeds of some of the plant disperse as seeds and some are dispersed in the form of fruits because they contain seeds inside them. There are various methods of seed dispersal that have been categorised into two main categories: Abiotic (like wind, gravity, water etc.) and Biotic (animal pollinators like insects).
Anemophily (wind pollination): It is the mode of transfer of pollen grains from anther to stigma through the agency of wind. The flowers that are wind pollinated are anemophilous. These flowers contains some adaptations like flowers are colourless, odourless and nectar-less; pollen grains are small, dry, dusty and sometimes saccate so that they can blow away easily to the long distances etc.
Hydrophily (water pollination): It is the mode of transfer of pollen grains from anther to stigma occurs through the agency water. The flowers that are water pollinated are hydrophilous flowers. These flowers contains some adaptations like flowers are small, colourless, odourless and nectar-less; pollen grains are unwettable, stigma are long and sticky etc. Dispersal by water takes place in some aquatic plants which is very rare and in some that grows near a water body. For example: Zostera, Hydrilla, Ceratophyllum etc.
Entomophily (insects pollination): It is the animal pollinator or biotic category in which the transfer of pollen grains from anther to stigma occurs through the agency of insects. The flowers that are insect pollinated are entomophilous flowers. These flowers contains some adaptations like flowers are usually large, brightly coloured and slowly to attract insect pollinators etc. The most common insect pollinators are as follows: moths, flies, butterflies, bees, beetles etc.
Dispersal by Humans: Human beings also help in dispersal of seeds during the farming.
There are much more methods for the dispersal of seeds like Ornithophily (pollination by birds), Chiropterophily (pollination by bats) etc.
Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down Across
(D) 1 : Thorough washing (A) 1 : Keeps warm
2 : Animal fibre 2 : Its leaves are eaten by silkworms
3 : Long thread like structure 3 : Hatches from egg of moth
Sketch the cross section of soil and label the various layers.
Here is a crossword puzzle: Good luck!
Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human body
Down
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water
Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2?
Sketch the reproductive parts of a flower.
Solve the following crossword puzzle with the clues given:
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
Describe how crystals of copper sulphate are prepared.
Match the items in Column I with those in Column II:
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight (v) Clayey soil (e) Lesser amount of humus
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Solve the following crossword puzzle with the clues given:
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
How does the process of fertilisation take place in flowers?
In addition to the rock particles, the soil contains
(i) air and water
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants
The water holding capacity is the highest in
(i) sandy soil
(ii) clayey soil
(iii) loamy soil
(iv) mixture of sand and loam
Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.
What are decomposers? Name any two of them. What do they do in the forest?
Explain how animals dwelling in the forest help it grow and regenerate.
Describe the function of the heart.
Match the items of Column I with suitable items in Column II
Column I Column II
(a) Salivary gland (i) Bile juice secretion
(b) Stomach (ii) Storage of undigested food
(c) Liver (iii) Saliva secretion
(d) Rectum (iv) Acid release
(e) Small intestine (v) Digestion is completed
(f ) Large intestine (vi) Absorption of water
(vii) Release of faeces
Explain why there is a need of variety of animals and plants in a forest.