REPRODUCTION IN ANIMALS

PRESENTATION BY :

REPRODUCTION IS THE ABILITY OF THE LIVING ORGANISMS TO PRODUCE YOUNG ONES SIMILAR TO THEMSELVES.

ANIMAL RERODUCTION IS OF TWO MAIN TYPES :

ASEXUAL REPRODUCTION SEXUAL REPRODUCTION

REPRODUCTION

THE PRODUCTION OF YOUNG ONES BY A SINGLE PARENT WITHOUT THE FORMATION AND FUSION OF GAMETES IS CALLED ASEXUAL REPRODUCTION.

ASEXUAL REPRODUCTION TAKES PLACE BY THE FOLLOWING PROCESSES:

BINARY FISSION MULTIPLE FISSION BUDDING

ASEXUAL REPRODUCTION

IT IS USUALLY OBSERVED IN UNICELLULAR ORGANISMS . A PARENT CELL DIVIDES INTO TWO DAUGHTER CELLS AND EACH CELL THUS, FORMED GROWS TO FORM AN INDIVISUAL. IT IS COMMON IN ORGANISMSB LIKE BACTERIA AND AMOEBA .

BINARY FISSION

IT IS THE REPEATED DIVISION OF A PARENT CELL INTO A NUMBER OF SMALL INDIVISUALS, e.g. PLASMODIUM ( MALARIAL PARASITE )

MULTIPLE FISSION

THE FORMATION OF A NEW INDIVISUAL FROM A SMALL PROTUBERANCE , THE BUD ARISING ON THE PARENT BODY IS CALLED BUDDING ,e.g. HYDRA AND YEAST .THE OFF SPRING REMAINS ATTACHED TO THE PARENT DURING ITS GROWTH. IT SEPARATES EVENTUALLY TO LIVE AS AN INDEPENDENT ORGANISM.

BUDDING

PRODUCTION OF YOUNG ONES BY THE FORMATION AND FUSION OF SPECIAL CELLS CALLED GAMETES, CONTRIBUTED GENERALLY BY TWO PARENTS , MALE AND FEMALE IS TERMED AS SEXUAL REPRODUCTION .

SEXUAL REPRODUCTION

IN MULTICELLULAR ORGANISMS , THE GAMETES ARE PRODUCED BY REPRODUCTIVE ORGANS. THE MALE GAMETES ARE CALLED THE SPERMS ARE PRODUCED BY THE MALE REPRODUCTIVE PART .

THE FEMALE GAMETES CALLED THE EGGS OR OVA ( SINGULAR-OVUM ) ARE PRODUCED BY THE FEMALE REPRODUCTIVE PART .

SPERM AND OVA

THE ANIMALS ARE OF THREE TYPES ON THE BASIS OF THE SITES OF THEIR FERTILIZATION AND DEVELOPMENT:

REPRODUCTIVE PATTERNS

PARENTS RELEASE SPERMS AND EGGS INTO THE SURROUNDING WATER , WHERE FERTILIZATION OCCURS AND ZYGOTES DEVELOP INTO OFFSPRINGS. FOR T HIS PATTERN TO SUCCEED , MALE AND FEMALE MUST SHED THEIR GAMETES AT THE SAME TIME AND IN LARGE NUMBERS, E.G. FROGS.

EXTERNAL FERTILIZATION AND

EXTERNAL DEVELOPMENT

SPERMS ARE PASSED FROM THE MALE INTO THE FEMALE BODY . THE FERTILIZATION TAKES PLACE WITHIN THE FEMALE BODY . THE ZYGOTE , AFTER ITS FORMATION , IS SURROUNDED BY SOME SECRETIONS , RESERVE FOOD AND E VEN A SHELL FOR DEVELOPMENT AND PROTECTION OF THE GROWING EMBRYO . THE DEVELOPMENT OF THE CHICK TAKES PLACE AFTER THE EGG HAS BEEN LAID , E.G. HEN .

INTERNAL FERTILIZATION AND

EXTERNAL DEVELOPMENT

BOTH FERTILIZATION AND DEVELOPMENT TAKE PLACE IN THE FEMALE BODY THIS MEANS THAT THE BOTH , FORMATION OF THE ZYGOTE AND DEVELOPMENT OF THE YOUNG ONE TAKE PLACE INSIDE THE BODY OF THE FEMALE , E.G. HUMAN BEINGS AND ELEPHANT .

INTERNAL FERTILIZATION AND

INTERNAL DEVELOPMENT

PARTHENOGENESIS IS A FORM OF ASEXUAL REPRODUCTION WITH FERTILIZATION. PARTHNOGENESIS OCCURS NATURALLY IN APHID, DAPHNIA, ROTIFERS, SOME INVERTIBRATES AND IN MANY PLANTS. IN MANY SOCIAL INSECTS, SUCH AS THE HONEYBEE AND THE ANT, THE UNFERTILIZED EGGS GIVE RISE TO THE MALE DRONES AND THE FERTILIZED EGGS TO THE FEMALE WORKERS AND A QUEEN. IT HAS ALSO BEEN OBSERVED IN SOME SNAKES, FISH AND MONITOR LIZARD.

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APHIDS AND ITS LIFE CYCLE

DAPHNIA AND ITS LIFE CYCLE

ROTIFERS

MALE REPRODUCTIVE SYSTEM INCLUDES A PAIR OF TESTS, A SCROTUM, TWO SPERM DUCTS,

URETHRA AND PENIS. TESTS ARE OVAL ORGANS PRESENT IN A SAC CALLED SCROTUM.THE

SPERMS DEVELOP IN THE TESTS. SPERMS PASS FROM THE TESTS THROUGH THE SPERM

DUCTS TO THE URETHRA. THE LAST PART OF THE URETHRA IS SURROUNDED BY A MUSCULAR

STRUCTURE CALLED THE PENIS. PENIS CONDUCTS URINE AS WELL AS SEMEN BUT

THE TWO CANNOT PASS THROUGH IT AT THE SAME TIME .

MALE REPRODUCTIVE SYSTEM

MALE REPRODUCTIVE SYSTEM

THE FEMALE REPRODUTION SYSTEM THE FEMALE REPRODUTION SYSTEM CONSISTS OF OVARIES, A PAIR OF OVIDUCTS, UTERUS AND VAGINA.

THE MAIN FUNCTION OF FEMALE REPRODUTION SYSTEM ARE TO PRODUSE EGGS, RECEIVE THE SPERMS, PROVIDE THE SITE FOR FERTILIZATION, ATTACHMENT OF THE GROWING EMBRYO TO THE UTERUS & DEVELOPMENT OF THE FOETUS.

FEMALE REPRODUCTIVE SYSTEM

OVARIES PRODUCE EGGS. AN EGG REACHES THE OVIDUCT

WHERE A SPERM FUSES WITH THE EGG AND A ZYGOTE IS FORMED. IT IS THIS ZYGOTE

THAT DIVIDES AND DEVELOPS TO FORM A YOUNG

ONE .OVARIES ALSO PRODUCE HORMONES THAT CONTROL THE PRODUCTION OF OVA.

THESE HORMONES ARE ALSO RESPONSIBLE FOR

MAINTENANCE OF PREGNANCY.

FEMALE REPRODUCTIVE SYSTEM

FEMALE REPRODUTION SYSTEM

IN VITRO FERTILIZATION (IVF) IS A PROCESS BY WHICH OVA ARE FERTILIZED BY SPERMS OUTSIDE THE FEMALE BODY. THE FERTILIZED EGG IS THEN TRANSFERRED TO THE UTERUS OF A WOMAN WITH THE INTENT TO ESTABLISH A SUCCESSFUL PREGNANCY. THE FIRST ‘TEST TUBE BABY ‘, LOUISE BROWN WAS BORN IN 1978 .

DO YOU KNOW

Lesley and John Brown were a young couple from Bristol who had been unable to conceive for nine years. Lesley Brown had blocked Fallopian tubes. Having gone from doctor to doctor for help to no avail, she was referred to Dr. Patrick Steptoe in 1976. On November 10, 1977, Lesley Brown underwent the very experimental in vitro fertilization procedure. The process had been a success! Though some wondered if the success had been more luck than science, continued success with the process proved that Dr. Steptoe and Dr. Edwards had accomplished the first of many "test-tube" babies.

 

ABOUT LOUISE BROWN

FERTILIZATION TAKES PLACE IN THE INITIAL PART OF THE OVIDUCT. THE SPERM AND OVUM FUSE THIS FUSION OF THE SPERM AND EGG IS CALLED FERTILIZATION. SINCE IT TAKES PLACE INSIDE THE BODY OF THE FEMALE, SO IT IS TERMED AS INTERNAL FERTILIZATION. DURING THIS PROCESS, THE NUCLEUI, OF THE SPERM AND EGG ALSO FUSE TO FORM A SINGLE NUCLEUS. THE RESULTANT SINGLE CELL FORMED AFTER FERTILIZATION IS CALLED A ZYGOTE .THUS , ZYGOTE CONTAINS NUCEAR PART OF THE FATHER AND OF THE MOTHER. THAT IS WHY, THE CHILD HAS SOME CHARACTERSTICS OF THE FATHER AND SOME OF THE MOTHER.

HOW DOES FERTILIZATION TAKES PLACE ?

IN HENS, FERTILIZATION IS INTERNAL AS IT TAKES PLACE INSIDE THE BODY OF THE FEMALE. BUT UNLKE HUMANS, THE DEVELOPMENT OF THE YOUNG ONE TAKES PLACE OUTSIDE THE BODY OF THE FEMALE BIRD. AFTER FERTILIZATION, THE ZYGOTE STARTS DIVIDING AND TRAVELS DOWN THE OVIDUCT. AS IT TRAVELS DOWN, A NUMBER OF PROTECTIVE LAYERS ARE FORMED AROUND IT. THE EGG SHELL IS ONE OF THE PROTECTIVE LAYERS AND IT IS DEPOSITED AROUND THE EGG IN THE LOWER PART OF THE OVIDUCT OF THE HEN, JUST BEFORE IT IS LAID.THE SHELL IS MADE OF CALCITE, A CRYSTALLINE FORM OF CALCIUM CARBONATE.

HOW DO HENS LAY EGGS

THE EMBRYO DEVELOPS INSIDE THE EGG FOR 21 DAYS, UNTIL A CHICK IS FULLY DEVELOPED. DURING THIS PERIOD, THE EGGS REQUIRE A SPECIFIC TEMPERATURE THAT IS PROVIDED BY THE HEN BY SITTING ON THESE EGGS. THEN THE EGG SHELL IS BROKEN AND THE CHICK COMES OUT.THIS IS CALLED HATCHING.

IN A LIFE CYCLE OF AN AMPHIBIAN, EGGS ARE LAID IN WATER. A TADPOLE THEN EMERGES FROM THE EGG, AND SWIMS FREELY IN WATER. THE TADPOLE HAS GILLS, A TAIL AND A SMALL CIRCULAR MOUTH. THE TADPOLE GROWS UNTIL IT BEGINS METAMORPHOSIS. METAMORPHOSIS BEGINS WITH THE DEVELOPMENT OF THE HIND LEGS, FOLLOWED BY THE FRONT LEGS. THE LUNGS DEVELOP, AND THE TADPOLE BEGINS TO SWIM TO THE SURFACE OF THE WATER TO BREATHE. THE INTESTINE SHORTENS TO ADAPT TO A CARNIVOROUS DIET. IN FROGS, THE TAIL IS ABSORBED BY THE BODY DURING THE LAST STAGES OF METAMORPHOSIS. A TAILED TADPOLE CHANGES INTO A TAIL - LESS FROG.

LIFE CYCLE OF FROG

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