Case Study Questions Class 8 Science Chapter 8 Reproduction in Animals
CBSE Class 8 Case Study Questions Science Reproduction in Animals. Important Case Study Questions for Class 8 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Reproduction in Animals.
At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.
CBSE Case Study Questions Class 8 Science Reproduction in Animals
Case study 1
Do you recall the processes ofdigestion, circulation andrespiration which you havestudied in your previous classes? Theseprocesses are essential for the survivalof every individual. You have also learntabout the process of reproduction inplants. Reproduction is essential for thecontinuation of a species. Imagine whatwould have happened if organisms hadnot reproduced. You will realise thatreproduction is very important as itensures the continuation of similarkinds of individuals, generation aftergeneration.Modes of Reproduction:Have you seen the young onesof different animals? Try to name someof the young ones by completing shown in examples at S. No.1 and 5.You must have seen the youngones of various animals being born.Can you tell how chicks andcaterpillars are born? How are kittensand puppies born? Do you think thatthese young ones looked the samebefore they were born as they do now?Let us find out.Just as in plants, there are two modesby which animals reproduce. These are:(i) Sexual reproduction, and(ii) Asexual reproduction.Sexual ReproductionTry to recall reproduction in plantswhich you studied in Class VII. You willremember that plants that reproducesexually have male and femalereproductive parts. Can you name theseparts? In animals also, males andfemales have different reproductive partsor organs. Like plants, the reproductiveparts in animals also produce gametesthat fuse to form a zygote. It is the zygotewhich develops into a new individual.This type of reproduction beginningfrom the fusion of male and femalegametes is called sexual reproduction.Let us find out the reproductive partsin humans and study the process ofreproduction in them.
S No. |
Animal | Young one |
1 | Human |
Baby |
2 |
Cat | Kitten |
3 | Dog |
Puppy |
4 |
Butterfly | Caterpillar |
5 | Hen |
Chick |
6 |
Cow | Calf |
7 | Frog |
Froglet |
Que. 1) Reproduction is essential for the continuation of a ………………………………………………………………………………………………...
(a) Genus
(b) Species
(c) Breed
(d) Group
Que. 2) Which among the following is the correct option stating the young one of butterfly?
(a) Caterpillar
(b) Calf
(c) Moth
(d) Chick
Que. 3) Calf is the young one of which of the following animals given below?
(a) Human
(b) Frog
(c) Hen
(d) Cow
Que. 4) Explain in detail term “sexual reproduction” in animals.
Que. 5) Name the two modes of reproduction in animals.
Answer Key
Que. 1) (b) Species
Que. 2) (a) Caterpillar
Que. 3) (d) Cow
Que. 4) Answer:In sexual reproduction, the reproductive parts produce gametes that fuse to form a zygote. The zygote develops into a new individual.
Que. 5) Answer: The two modes of reproduction in animals include: i) Sexual reproduction ii) Asexual reproduction
Case study 2
Male Reproductive Organs: The male reproductive organs include apair of testes (singular, testis), two spermducts and a penis. The testesproduce the male gametes calledsperms. Millions of sperms are producedby the testes. Thoughsperms are very small in size, each hasa head, a middle piece and a tail. Doesit appear to be a single cell? Indeed, eachsperm is a single cell with all the usualcell components.Female Reproductive Organs:The female reproductive organs are a pairof ovaries, oviducts (fallopian tubes) andthe uterus. The ovary producesfemale gametes called ova (eggs). In human beings, a singlematured egg is released into the oviductby one of the ovaries every month.Uterus is the part where development ofthe baby takes place. Like the sperm,an egg is also a single cell.Fertilisation: The first step in the process ofreproduction is the fusion of a spermand an ovum. When sperms come incontact with an egg, one of the spermsmay fuse with the egg. Such fusion ofthe egg and the sperm is calledfertilisation. Duringfertilisation, the nuclei of the sperm andthe egg fuse to form a single nucleus.This results in the formation of afertilised egg or zygote. Didyou know that the zygote is thebeginning of a new individual?The process of fertilisation is themeeting of an egg cell from the motherand a sperm cell from the father. So,the new individual inherits somecharacteristics from the mother andsome from the father. Look at yourbrother or sister. See if you can recognisesome characters in them similar to thoseof your mother or your father.Fertilisation which takes place insidethe female body is called internalfertilisation. Internal fertilisationoccurs in many animals includinghumans, cows, dogs and hens.Boojho and Paheli’s teacher once toldthem in the class that in some womenoviducts are blocked. These womenare unable to bear babies becausesperms cannot reach the egg forfertilisation. In such cases, doctorscollect freshly released egg andsperms and keep them together for afew hours for IVF or in vitrofertilisation (fertilisation outside thebody). In case fertilisation occurs,the zygote is allowed to develop forabout a week and then it is placed inthe mother’s uterus. Completedevelopment takes place in the uterusand the baby is born like any otherbaby. Babies born through thistechnique are called test-tubebabies. This term is actuallymisleading because babies cannotgrow in test tubes.You will be surprised to know thatin many animals’ fertilisation takesplace outside the body of the female.In these animals, fertilisation takesplace in water. Let us find out howthis happens.During spring or rainy season, frogsand toads move to ponds and slow-flowing streams. When the male andfemale come together in water, thefemale lays hundreds of eggs. Unlikehen’s egg, frog’s egg is not covered by ashell and it is comparatively verydelicate. A layer of jelly holds the eggstogether and provides protection to theeggs.As the eggs are laid, the maledeposits sperms over them. Eachsperm swims randomly in water withthe help of its long tail. The spermscome in contact with the eggs. Thisresults in fertilisation. This type offertilisation in which the fusion of amale and a female gamete takes placeoutside the body of the female is calledexternal fertilisation. It is verycommon in aquatic animals such asfish, starfish, etc.
Que. 1) Which of the following is NOT a part of the female reproductive system?
(a) Fallopian tube
(b) Ovaries
(c) Testes
(d) Uterus
Que. 2) The type of fertilisation in which the fusion of male and female gametes takes place outside the body is called ………………………………………………………………………………………...
(a) Internal fertilisation
(b) External fertilisation
(c) Systemic fertilisation
(d) Directional fertilisation
Que. 3) Which among the following is the correct full form of IVF?
(a) in voluntary fertilisation
(b) inter vesicular fistula
(c) intra venous fertilisation
(d) in vitro fertilisation
Que. 4) Define the process of fertilisation in detail.
Que. 5) What are test tube babies?
Answer Key
Que. 1) (c) Testes
Que. 2) (b) External fertilisation
Que. 3) (d) in vitro fertilisation
Que. 4) Answer: When sperms come in contact with the egg, one of the sperm fuses with egg to form a zygote, the process is called fertilisation. The nuclei of sperm from male and the nuclei of ovum from female fuse to form a single fertilised egg or zygote.
Que. 5) Answer:The eggs and sperms are taken out from the human body and are kept together for few hours for in vitro fertilisation. In case fertilisation occurs, the zygote is allowed to develop for a week and then placed in the mother’s uterus. And the baby thus formed is called a test tube baby.
Case study 3
How could a single cellbecome such a bigindividual?Development of Embryo:Fertilisation results in the formation ofzygote which begins to develop into anembryo. The zygote dividesrepeatedly to give rise to a ball of cells. The cells then begin to formgroups that develop into different tissuesand organs of the body. This developingstructure is termed an embryo. Theembryo gets embedded in the wall of theuterus for further development.The embryo continues to develop inthe uterus. It gradually develops bodyparts such as hands, legs, head, eyes,ears etc. The stage of the embryo inwhich all the body parts can beidentified is called a foetus.When the development of the foetus iscomplete, the mother gives birth tothe baby.Internal fertilisation takes place inhens also. But, do hens give birth tobabies like human beings and cows? Youknow that they do not. Then, how arechicks born? Let us find out.Soon after fertilisation, the zygotedivides repeatedly and travels down theoviduct. As it travels down, manyprotective layers are formed around it.The hard shell that you see in a hen’segg is one such protective layer.After the hard shell is formed aroundthe developing embryo, the hen finallylays the egg. The embryo takes about 3weeks to develop into a chick. You musthave seen the hen sitting on the eggs toprovide sufficient warmth. Did you knowthat development of the chick takesplace inside the egg shell during thisperiod? After the chick is completelydeveloped it bursts open the egg shell.In animals which undergo externalfertilisation, development of the embryotakes place outside the female body. Theembryos continue to grow within theiregg coverings. After the embryos develop,the eggs hatch. You must have seennumerous tadpoles swimming in pondsand streams.Viviparous and Oviparous Animals: We have learnt that some animals givebirth to young ones while some animalslay eggs which later develop into youngones. The animals which give birth toyoung ones are called viviparousanimals. Those animals which lay eggsare called oviparous animals. Thefollowing activity will help youunderstand better and differentiatebetween viviparous and oviparousanimals.The eggs of a few animals are easyto observe because their mothers laythem outside their bodies. These areexamples of oviparous animals. But youwould not be able to collect the eggs ofa dog, cow or cat. This is because theydo not lay eggs. The mother gives birthto the young ones. These are examplesof viviparous animals.Young Ones to Adults: The new individuals which are born orhatched from the eggs continue to growtill they become adults. In someanimals, the young ones may look verydifferent from the adults. Recall the lifecycle of the silkworm (egg → larva orcaterpillar → pupa → adult) you studiedin Class VII. Frog is another suchexample.Observe the different stages of frogstarting from the egg to the adult stage.We find that there are three distinctstages, that is, egg → tadpole (larva) →adult. Don’t the tadpoles look sodifferent from the adults? Can youimagine that these tadpoles would someday become frogs? Similarly, thecaterpillar or the pupa of silkworm looksvery different from the adult moth. Thefeatures that are present in the adult arenot found in these young ones. Then whathappens to the tadpoles or caterpillarsthereafter?You must have seen a beautiful mothemerging out of the cocoon. In the case oftadpoles, they transform into adultscapable of jumping and swimming. Thetransformation of the larva into an adultthrough drastic changes is calledmetamorphosis. What about the changesthat we observe in our body as we grow?Do you think we too undergometamorphosis? In human beings, bodyparts similar to those present in the adultsare present from the time of birth.
Que. 1) The developing zygote called the embryo gets embedded in which part of the female reproductive system?
(a) Oviduct
(b) Wall of uterus
(c) Cervix
(d) Ovary
Que. 2) Complete the missing stage in the life cycle of silkworm: egg→ larva or caterpillar→ …………………………………………………………………………. →Adult
(a) Pupa
(b) Moth
(c) Tadpole
(d) Nymph
Que. 3) Which among the following is NOT an example of viviparous animals?
(a) Monkey
(b) Cow
(c) Dog
(d) Frog
Que. 4) Define the term “metamorphosis”.
Que. 5) What do you mean by oviparous animals? Give one example.
Answer Key
Que. 1) (b) Wall of uterus
Que. 2) (a) Pupa
Que. 3) (d) Frog
Que. 4) Answer: The transformation of larvae into an adult through drastic changes is called the process of metamorphosis.
Que. 5) Answer: The animals which lay eggs and the egg later develops into an adult id called oviparous animals. Example of oviparous animals include chicks and most of the birds.
Case study 4
Asexual Reproduction: So far, we have learnt about reproductionin some familiar animals. But whatabout very small animals like hydra andmicroscopic organisms like amoeba? Doyou know how they reproduce? Let usfind out.In each hydra, there may be one ormore bulges. These bulges are thedeveloping new individuals and they arecalled buds. Recall the presence of budsin yeast. In hydra too the new individualsdevelop as outgrowths from a singleparent. This type of reproduction inwhich only a single parent is involved iscalled asexual reproduction. Since newindividuals develop from the buds inhydra, this type of asexual reproductionis called budding.Anothermethodofasexualreproduction is observed in themicroscopic organism, amoeba. Let ussee how this happens.You have already learnt about thestructure of amoeba. You will recall thatamoeba is a single-celled organism. It begins the process ofreproduction by the division of itsnucleus into two nuclei.This is followed by division of its bodyinto two, each part receiving a nucleus. Finally, two amoebae areproduced from one parent amoeba. This type of asexualreproduction in which an animalreproduces by dividing into twoindividuals is called binary fission.Apart from budding and binary fission,there are other methods by which asingle parent reproduces young ones.You will study about these in yourhigher classes.Story of Dolly, the Clone: Cloning is the production of an exact copy of a cell, any other living part, or acomplete organism. Cloning of an animal was successfully performed for the firsttime by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh,Scotland. They successfully cloned a sheep named Dolly. Dolly wasborn on 5th July 1996 and was the first mammal to be cloned.During the process of cloning Dolly, a cell was collected from the mammary glandof a female Finn Dorsett sheep. Simultaneously, an egg was obtainedfrom a Scottish blackface ewe. The nucleus was removed from theegg. Then, the nucleus of the mammary gland cell from the Finn Dorsett sheepwas inserted into the egg of the Scottish blackface ewe whose nucleus had beenremoved. The egg thus produced was implanted into the Scottish blackface ewe.Development of this egg followed normally and finally Dolly was born. ThoughDolly was given birth by the Scottish blackface ewe, it was found to be absolutelyidentical to the Finn Dorsett sheep from which the nucleus was taken. Since thenucleus from the egg of the Scottish blackface ewe was removed, Dolly did notshow any character of the Scottish blackface ewe. Dolly was a healthy clone ofthe Finn Dorsett sheep and produced several offspring of her own through normalsexual means. Unfortunately, Dolly died on 14th February 2003 due to a certainlung disease.Since Dolly, several attempts have been made to produce cloned mammals.However, many die before birth or die soon after birth. The cloned animals aremany-a-times found to be born with severe abnormalities.
Que. 1) The process in which the bulges in the body of Hydra called the buds develop into a new individual is called …………………………………………………………………………………………….
(a) Binary fission
(b) Bulbs
(c) Budding
(d) Budging
Que. 2) Dolly was a healthy clone of which of the following sheep?
(a) Finn Dorsett sheep
(b) Scottish blackface ewe
(c) Suffolk
(d) Cheviot
Que. 3) In which of the following year did Ian Wilmut successfully cloned a Sheep named Dolly?
(a) 1996
(b) 1997
(c) 2003
(d) 1995
Que. 4) Define the process of “asexual reproduction”.
Que. 5) What is the process of cloning?
Answer Key
Que. 1) (c) Budding
Que. 2) (a) Finn Dorsett sheep
Que. 3) (a) 1996
Que. 4) Answer: The type of reproduction in which only a single parent is involved is known as asexual reproduction. Budding is one of the examples of asexual reproduction.
Que. 5) Answer: Cloning is the production of the exact copy of the cell, any other living part or a complete organism. The first successfully cloned animal is a sheep named Dolly.