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Karnataka State Syllabus Class 8 Science Important Questions Chapter 20 Reproduction in Higher Plants
Question 1.
Define life processes.
Answer:
All living organisms will have to carry out certain basic activities in order to maintain and sustain life. Such vital processes in living organisms are called life processes.
Question 2.
Which are the basic life processes?
Answer:
The basic life processes common to all living beings include movement, respiration, response to stimuli, growth, reproduction, excretion and nutrition.
Question 3.
What is meant by reproduction?
Answer:
Reproduction is a biological process in which an organism gives rise to young ones (offspring) similar to itself. Reproduction enables the continuity of the species, generation after generation.
Question 4.
Explain the importance of reproduction in organisms.
Answer:
Reproduction is a very important life process. Organisms reproduce to produce young ones like themselves. Thus, reproduction helps them to carry on their generation. The characteristics are passed on from parents to the next generation through the process of reproduction.
If reproduction does not take place, no living being will survive on the earth. Reproduction is important for the survival of all species. Without reproduction, species perish and life would come to an end.
Question 5.
Which are the two basic modes of reproduction found in living organisms?
Answer:
The two basic modes of reproduction found in living organisms are
- Asexual reproduction
- Sexual reproduction.
Question 6.
What is asexual reproduction? Give an example.
Answer:
The mode of reproduction which does not involve the fusion of male sex cell and female sex cell is called asexual reproduction. For example, amoeba reproduces by binary fission. The parent cell divides itself into two or more daughter cells. This process does not involve the fusion of male sex cell and the female sex cell. This is a case of asexual reproduction.
Question 7.
In which groups of organisms do we generally find asexual methods of reproduction?
Answer:
Asexual modes of reproduction are generally found in lower organisms such as monerans, protistans, algae and fungi.
Question 8.
What is sexual reproduction? Give examples of organisms which reproduce sexually.
Answer:
The mode of reproduction which involves the fusion of the male sex cell and the female sex cell is called sexual reproduction. It involves the formation and fusion of specialised reproductive cells called gametes.
We find sexual reproduction in higher animals and flowering plants. eg: Organisms like elephant, dog, humans, mango plant, mustard plant reproduce sexually.
Question 9.
What are the modes of reproduction in which green plants produce young ones of their own kind?
Answer:
We find both sexual method and vegetative method of reproduction in green plants.
Question 10.
What are gametes? How many types of gametes are there?
Answer:
Specialized cells which are directly involved in the process of reproduction in higher order plants and animals are called gametes. They are also called sex cells. There are two types of gametes. Male gamete and female gamete. The male gamete is called sperm and the female gamete is called ovum (also called egg).
Question 11.
What is fertilization?
Answer:
The fusion of the male sex cell and the female sex cell resulting in a cell which develops into a new organism is called fertilization.
Question 12.
What are the advantages of sexual reproduction?
Answer:
Sexual reproduction promotes genetic variability, favours the development of adaptive features, and speeds up evolution.
Question 13.
In which group of green plants do we find sexual mode of reproduction?
Answer:
We find sexual mode of reproduction in flowering plants which are also known as angiosperms.
Question 14.
What are angiosperms? Give four examples.
Answer:
Highly evolved vascular plants in which seeds are enclosed inside the fruit are called angiosperms. These are commonly called flowering plants. eg: Mustard plant, wheat plant, horse gram, bean plant, pea plant, etc.
Question 15.
Why do we say that angiosperms are higher order plants?
Answer:
Angiosperms are the common flowering plants. They are most successful because they have highly advanced reproductive systems. They have flowers which contain male and female reproductive organs. They even produce sex cells. This is why angiosperms are called higher order plants.
Question 16.
Which are the organs of reproduction in higher order plants?
Answer:
The organs of reproduction in higher order plants are flowers.
Question 17.
From which part of a plant do flowers usually emerge?
Answer:
Flowers generally emerge from the axil of a leaf called bract. The flowers are generally borne on a stalk called pedicel.
Question 18.
Are there plants which do not produce flowers? If so, how do they reproduce?
Answer:
There many species of plants which do not produce flowers. They reproduce by asexual methods.
Question 19.
Which are the three major steps involved in reproduction in angiosperms? Explain.
Answer:
Angiosperms reproduce by sexual method. Reproduction in angiosperms involves three steps.
1. Gamete formation and gamete transfer:
Gamete formation is the first process to occur during sexual reproduction. Male gametes develop in stamens through the formation of pollen grains. Similarly, female gametes (egg cells) develop inside the ovary of carpels. Once the gametes are formed, pollination or the process of transfer of pollen grains from the anther to the stigma occurs.
2. Fertilization:
It is the second major event during sexual reproduction. The process which follows pollination is called fertilization. It involves the fusion of the haploid male gamete in the pollen grain with the haploid female gamete in the ovule. To bring about fertilization, the pollen grains which get deposited on the stigma of the carpel must penetrate the style and reach the ovule.
Hence, each pollen grain produces a projection called pollen tube which grows through the length of the style and finally reaches the ovule. The pollen tube enters the ovule and delivers the male gamete. Inside the ovule, there is a structure called embryo sac which encloses the female gamete. Then male gamete and female gamete unite resulting in the formation of a zygote. This process is fertilization.
3. Development:
Development of zygote into a young plant is the third and final event in sexual reproduction. Development involves various steps First, the zygote develops into an embryo that later differentiates into a seed and grows into a new plant.
Surrounding the embryo, a nutritive tissue called endosperm is formed. The ovule becomes the seed. The coverings of the ovule transform into the seed coat. The ovary portion of the carpel gets transformed into the fruit enclosing the seed. Petals, sepals and other parts of the flower fall off.
Question 20.
Draw a neat labelled diagram of a typical flower.
Answer:
Question 21.
Which are the four prominent whorls that you see in a typical flower as you look from outside to inside?
Answer:
We see four prominent whorls in a typical flower as we move from outside to inside. These are calyx, corolla, androecium and gynoecium.
Question 22.
What is calyx? What is it made of?
Answer:
The outermost whorl of a flower is called calyx. It is made up of green coloured units called sepals.
Question 23.
What is the function of calyx?
Answer:
The function of the calyx (sepals) is to protect the flower, especially in the bud condition.
Question 24.
What is corolla? What is it composed of? What is its function?
Answer:
As we move from outside towards inside of a flower, the second whorl is called corolla. It is composed of bright coloured segments called petals. The basic function of corolla (petals) is to attract insects, beetles and other organisms to the flower for pollination. The corolla also gives some protection to the reproductive parts.
Question 25.
What is androecium? What are they made of? What is their function?
Answer:
As we move from outside towards inside of a flower, the third whorl is called androecium. It is the male reproductive organ in a flower. Androecium is made up of structures called stamens. Each stamen is made up of a filament and anther.
Anther is a sac-like structure at the top of the filament filled with pollen grains. The chief function of androecium is to produce pollen grains which contain male gametes.
Question 26.
What is gynoecium? What is it made of? What are its functions?
Answer:
The innermost whorl of a flower is called gynoecium. It is the female reproductive part in a flower. Gynoecium consists of a set of carpels. Each carpel consists of an ovary, which contains one or more ovules, a style and the stigma. The female gametes are found in the ovules.
The ovary is at the base of the flower. A tubular structure that extends from the ovary is called the style. The top of the style is a surface called stigma which receives pollens.
Question 27.
What are the functions of the parts of carpel in a flower?
Answer:
A carpel in a flower consists of ovary, style and stigma. The ovary of a carpel produces ovules. The ovule contains the female gametes, ova. The ovary protects the ovule and, once fertilisation occurs, it will become the fruit.
The stalk of a carpel is a tubular structure between the stigma and the ovary. The stalk helps the movement of pollens from the stigma to the ovary. Stigma is the receptacle for pollen. It has a sticky surface so that pollens stick. The stigma also transports the pollen to the ovum for fertilization.
Question 28.
What is meant by pollination? Mention its importance in reproduction.
Answer:
The process of transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower is called pollination. Pollination is a prerequisite for fertilization. Seeds cannot form without pollination.
Question 29.
Which are the two types of pollination found in plants?
Answer:
The two types of pollination found in plants are
- Self pollination
- Cross pollination.
Question 30.
Distinguish between self pollination and cross pollination.
Answer:
The transfer of pollen from the anthers of a flower to the stigma of the same flower is called self pollination. The transfer of pollen from the anthers of a flower to the stigma of another flower of the same plant or a different plant of the same species is called cross pollination.
Question 31.
What is the role of wind, water, insects and animals in the process of pollination?
Answer:
Most plants need help to transport pollens from one flower to the pistil of another. Wind moves the pollens for some plants like com. Insects, birds and mammals help to transfer pollens to the stigma of flowers in most other plants.
Question 32.
Give two examples for abiotic agents of pollination.
Answer:
Wind and water are examples of abiotic agents of pollination.
Question 33.
What are pollinators? Give examples.
Answer:
Animals that move pollens from the anthers to the stigmas of flowers are called pollinators. They are called so because they assist in pollination. Animals that are known to be good pollinators include bees, butterflies, humming birds, moths, some flies, some wasps, and nectar-feeding bats.
Question 34.
From among self pollination and cross pollination, which is more common in nature? Why?
Answer:
In nature, cross pollination is more common than self pollination. This type of pollination has many advantages. For instance, it allows for diversity in the species, as it combines genetic information from different plants. Cross pollination hastens the process of evolution. Individuals of the species in successive generations become more adaptive to the environment.
Question 35.
Give examples for plants in which pollination is facilitated by water.
Answer:
Generally, water acts as an agent of pollination in aquatic plants. Water assists pollination in aquatic plants like Vallisneria, Hydrilla and Elodea.
Question 36.
In which type of plants does wind act as an agent of pollination? Give examples.
Answer:
Wind acts as an agent of pollination in plants which bear small, dull coloured flowers. Such flowers probably cannot attract insects and birds to effect pollination. eg: Sugarcane, maize, grasses, etc.
Question 37.
What adaptations do you see in flowers to attract pollinators like insects, birds and beetles?
Answer:
Flowers have evolved to produce fragrances which draw pollinators towards them. Flowers of some plants have highly attractive colours, shape or size which helps to attract animals towards them. Some flowers produce nectar which is a great attraction for insects and bees.
Question 38.
Define fertilization. Where does fertilization actually occur in higher plants?
Answer:
The union of male gamete and female gamete to form a single cell is called fertilization. Fertilization in higher plants occurs in the ovaries of the carpel.
Question 39.
How do pollens reach the ovaries of a flower? Explain.
Answer:
Pollen somehow gets deposited on the stigma of the carpel. For fertilization to occur, these pollens must reach the ovule through the style. The pollen grains on the stigma of a flower will develop a pollen tube that extends up to the ovule through the style.
Pollens which carry the male sex cells will now move through the pollen tube. Once the pollen tube reaches an ovule, it delivers sperm cells with a burst which goes to the embryo sac. The sperm cell fertilizes the egg cell to form an embryo, which will develop into a seed. The seed is the future plant.
Question 40.
What is a zygote?
Answer:
A single cell formed by the union of the male gamete and the female gamete is called zygote.
Question 41.
What changes occur in the flower after pollination and fertilization?
Answer:
After pollination and fertilization gets over, the following changes occur in the flower:
- The embryo develops into a seed which can later grow into a new plant.
- A nutritive tissue called endosperm develops around the embryo.
- The covering of the ovule forms the seed coat.
- Ovary part of the carpel gets transformed into a fruit enclosing the seed.
- Sepals, petals and other parts of the flower will fall off.
Question 42.
Which part of the flower develops into a seed and the seed coat?
Answer:
The fertilized ovum develops into an embryo from which a seed is formed. The seed coat is formed from the tough coverings of the ovule.
Question 43.
Which is the end product of pollination and fertilization in plants?
Answer:
Formation of seed is the end product of pollination and fertilization.
Question 44.
What are pulses? Give examples.
Answer:
The edible seeds of various leguminous plants are called pulses. E.g. Green pea, lentil, black gram, horse gram, cowpea, etc.
Question 45.
What is pod of a pulse plant?
Answer:
The Seeds of pulses occur inside an elongated seed vessel which splits open on both sides when it becomes ripe. Such seed vessels of leguminous plants are called pods.
Question 46.
Give examples for commonly used food grains. To which family do the grain crops belong?
Answer:
Maize, rice, wheat, barley, oats and sorghum are some of the commonly used food grains. These crops belong to the family called Poaeceae.
Question 47.
Distinguish between cereals and pulses.
Answer:
Cereal crops or grains arc mostly monocot grasses cultivated for their edible grains. Cereal grains provide more energy worldwide than any other type of crop. They are also a rich source of carbohydrate. They belong to the family Poaeceae.
On the other hand, pulses are dicot crops yielding seeds of variable size, shape and colour within a pod. They have high protein and essential amino acid content. They belong to the family Leguminosae.
Question 48.
What are millets? What is their speciality? Give examples for millets.
Answer:
Millet refers to a variety of grasses which yield cereal grains that are smaller in size. Millet grows well on poorly fertilized and dry soils and fits well into hot climates with poor rainfall. Most of these belong to the family Gramineae or Poaceae. eg: Jowar, Bajra (pearl millet), Ragi, etc.
Question 49.
Give one word for the following
- Nutritive tissue in the seed.
- Structure in which pollen grains are produced.
- Process involving transfer of pollen grains from anther to stigma.
- Process that brings about fusion of male and female gametes.
Answer:
- Endosperm.
- Anther.
- Pollination.
- Fertilization.
Multiple Choice Questions
Question 1.
Seeds develop from
(a) ovary
(b) ovule
(c) embryo
(d) embryo sac
Answer:
(b) ovule
Question 2.
Which of the following is not a part of the innermost whorl of the flower?
(a) style
(b) pistil
(c) stigma
(d) ovary
Answer:
(b) pistil
Question 3.
From among the sets of terms given below, those that are associated with the gynoecium are
(a) Stigma, ovule, embryo sac, placenta
(b) Thalamus, pistil, style, ovule
(c) Ovule, ovary, embryo sac, corolla
(d) Ovule, stamen, ovary, embryo sac
Answer:
(d) Ovule, stamen, ovary, embryo sac
Question 4.
Colour of night blooming flowers is usually
(a) violet
(b) red
(c) yellow
(d) whitish
Answer:
(d) whitish
Question 5.
You have been asked to collect plant sperm for a new plant breeding program in a laboratory. Which of the following tissues would be a good source of sperms?
(a) anther
(b) ovary
(c) pedicel
(d) petals
Answer:
(a) anther
Question 6.
A particular species of plants produce light, non-sticky pollen in large numbers and its stigmas are long and feathery. The pollination in such plants occur through
(a) insects
(b) water
(c) wind
(d) animals.
Answer:
(c) wind
Question 7.
The correct sequence of reproductive states seen in flowering plants is
(a) gametes, zygote, embryo, seedling
(b) zygotes, gametes, embryo, seedling
(c) seedling, embryo, zygote, gametes
(d) gametes, embryo, zygote, seedling
Answer:
(a) gametes, zygote, embryo, seedling
Question 8.
Which of the following is not directly involved in the process of reproduction in angiosperms
(a) stigma
(b) sepal
(c) carpel
(d) style
Answer:
(b) sepal
Question 9.
The part of the flower that produces pollen is
(a) ovary
(b) petal
(c) anther
(d) pistil
Answer:
(c) anther
Question 10.
The anther contains
(a) ovules
(b) female gametes
(c) ovary
(d) pollen grains
Answer:
(d) pollen grains
Question 11.
Pollination refers to the
(a) transfer of pollen from anther to ovary
(b) transfer of male gametes from anther to stigma
(c) transfer of pollen from anther to stigma
(d) transfer of pollen from anther to ovule
Answer:
(c) transfer of pollen from anther to stigma
Fill In The Blanks
- Flowers with blue petals, nectar and strong scent are most likely to be pollinated by bees
- The male reproductory part in a flower is called Androecium
- Variations in the offspring is the characteristic of sexuall reproduction,
- There is much wastage of pollen grains in wind pollination,
- Fertilization eventually leads to the formation of seed
- A fertilized ovum is called zygote
- The female sex cells in plant are produced in ovule
- Most pulses belong to the family leguminosae
- The sexual reproduction involves pollination and fertilization
- The type of pollination that is common in nature is cross pollination
- A male reproductive cell is called sperm
- The process of formation of a single cell by the union of male gamete and female gamete is known as fertilization
Match The Following
| A | B |
| 1. Calyx | a. consists of carpel |
| 2. Corolla | b.consists of sepals |
| 3. Androecium | c. consists of zygote |
| 4. Gynoecium | d. consists of petals |
| e. consists of millets 0 | |
| f. consists of stamens |
Answer:
1 – b, 2 – d, 3 – f, 4 – a.
| A | B |
| 1. Ovule | a. attract pollinators through their colours |
| 2. Pollen tube | b.produces pollen grains |
| 3. Stamens | c. is the other name for a seed |
| 4. Petals | d. extends from the stigma to the ovule |
| e. made of anther and filament | |
| f. the part where fertilization occurs | |
| g. pollinators die when they eat |
Answer:
1 – f, 2 – d, 3 – e, 4 – a.