Topics
Reproduction
Biotechnology - Principles and Processes
Principles of Inheritance and Variation
- Principles of Inheritance and Variation Introduction
- Mendel’s Laws of Inheritance
- Monohybrid Cross - Inheritance of One Gene
- Law of Dominance
- Law of Segregation
- Law of Segregation - Incomplete Dominance
- Law of Segregation - Co-dominance
- Dihybrid Cross - Inheritance Two Genes and Law of Independent Assortment
- Mendel’s Laws of Inheritance
- Chromosomal Theory of Inheritance
- Linkage and Crossing Over
- Introduction of Sex Determination
- Sex Determination
- Concept of Mutation
- Pedigree Analysis
- Genetic Disorders
- Genetic Disorders
- Elementary Idea of Polygenic Inheritance
- Deviations from Mendelism - Incomplete Dominance, Co-dominance, Multiple Alleles and Inheritance of Blood Groups, Pleiotropy
- Heredity and Variation
- Sex Determination in Birds
- Sex Determination in Honey Bees
- Principles of Inheritance and Variation Question
Human Health and Diseases
- Introduction of Human Health and Diseases
- Common Diseases in Humans
- Immunity
- Types of Immunity: Innate or Inborn (Inherited) Immunity and Acquired or Adaptive Immunity
- Vaccination and Immunization
- Allergy
- Autoimmunity
- Immune System in the Body
- Sexually Transmitted Diseases (STD)
- Cancer
- Introduction of Drugs and Alcohol Abuse
- Adolescence - Drug and Alcohol Abuse
- Addiction and Dependence
- Effects of Drug / Alcohol Abuse
- Prevention and Control of Drugs and Alcohol Abuse
- Infectious and Non Infectious Disease
- Maintaining Good Health, Yoga, Excercise
- Human Health and Diseases (Questions)
Organisms and Populations
- Introduction of Organisms and Populations
- Ecology (Organism, Population, Community and Biome)
- Introduction of Organisms and Environment
- Major Abiotic Factors
- Responses to Abiotic Factors
- Adaptations and Its Types
- Population Attributes
- Population Growth
- Life History Variation
- Population Interactions
- Population and Ecological Adaptations
- Organisms and Populations (Questions)
Reproduction in Organisms
- Life Span of Organisms
- Maximum Life Span of Organisms
- Reproduction in Organisms
- Types of Reproduction
- Asexual Reproduction
- Asexual Reproduction in Plant
- Asexual Reproduction in Animal
- Sexual Reproduction
- Different Phases in Sexual Reproduction
- Events in Sexual Reproduction in Organisms
- Pre-fertilisation Events in Organisms
- Fertilisation in Organisms
- Post-fertilisation Events in Organisms
Biotechnology and Its Application
Strategies for Enhancement in Food Production
- Introduction of Strategies for Enhancement in Food Production
- Animal Husbandry (Livestock)
- Dairy Farming (Cattle Farming)
- Poultry Farming
- Apiculture (Bee Farming)
- Pisciculture (Fish Farming)
- Animal Breeding
- Plant Breeding
- Single Cell Protein (SCP)
- Tissue Culture
- Strategies for Enhancement in Food Production (Questions)
Ecosystem
Genetics and Evolution
Sexual Reproduction in Flowering Plants
- Flower - a Fascinating Organ of Angiosperms
- Sexual Reproduction in Flowering Plants
- Androecium: Male Reproductive Organ
- Gynoecium: Female Reproductive Organ
- Pollination
- Kinds of Pollination
- Agents of Pollination
- Outbreeding Devices
- Pollen Pistil Interaction
- Artificial Hybridization
- Double Fertilization in Plants
- Development of Endosperm
- Development of Embryo
- Seed from Ovule
- Fruit from Ovary
- Polyembryony
Molecular Basis of Inheritance
- Introduction of Molecular Basis of Inheritance
- Structure of Polynucleotide Chain
- Packaging of DNA Helix
- Introduction of Search for Genetic Material
- The Genetic Material is a DNA
- Properties of Genetic Material (DNA Versus RNA)
- Concept of RNA World
- The Experimental Proof
- The Machinery and the Enzymes
- Introduction of Transcription
- Transcription Unit
- Transcription Unit and the Gene
- Types of RNA and the Process of Transcription
- Introduction of Genetic Code
- Mutations and Genetic Code
- tRNA – the Adapter Molecule
- Concept of Translation
- Introduction of Regulation of Gene Expression
- The Lac Operon
- Human Genome Project
- DNA Fingerprinting Technique
- Structure of DNA and RNA
- Structure of Nucleotide
- Rice Genome Project
- Molecular Basis of Inheritance (Questions)
Human Reproduction
- Human Reproduction Introduction
- Male Reproductive System
- Female Reproductive System
- Gametogenesis in Animal
- Menstrual Cycle (Ovarian Cycle)
- Fertilisation and Implantation
- Pregnancy and Embryonic Development
- Parturition and Lactation
- Microscopic Anatomy of Testis
- Microscopic Anatomy of Ovary
- Embryo Development Upto Blastocyst Formation
- Human Reproduction Questions
Evolution
- Origin and Evolution of Universe and Earth
- Origin of Life (Theories)
- Evolution of Life Forms - a Theory
- Evidence of Organic Evolution
- Adaptive Radiation
- Biological Evolution
- Mechanism of Organic Evolution
- Hardy Weinberg’s Principle
- Brief Account of Evolution
- Human Evolution
- Theories of Evolution: Darwinism or Theory of Natural Selection
- Micro and Macro Evolution
- Speciation
- Evolution Stages
- Modern Synthetic Theory of Evolution
- Gene Flow and Genetic Drift
- Evolution (Questions)
Microbes in Human Welfare
Biodiversity and Its Conservation
Biology and Human Welfare
Environmental Issues
- Environmental Issues
- Prevention of Air Pollution
- Controlling Vehicular Air Pollution: a Case Study of Delhi
- Introduction of Water Pollution and Its Control
- Domestic Sewage and Industrial Effluents
- A Case Study of Integrated Waste Water Treatment
- Concept of Solid Wastes
- Agrochemicals and Their Effects
- Radioactive Wastes
- Greenhouse Effect and Climate Change
- Ozone Depletion in the Stratosphere
- Degradation by Improper Resource Utilisation and Maintenance
- Deforestation and Its Causes
- Radioactive Waste Management and E-waste
- Solid Waste Management
- Noise Pollution
- Environmental Issues
Biotechnology and Its Applications
Reproductive Health
Ecology and Environment
description
- Pre-fertilisation Events in Organisms:
- Gametogenesis - Sexuality in organisms, Cell division during gamete formation
- Gamete Transfer
notes
Pre-fertilisation Events in Organisms:
- These include all the events of sexual reproduction prior to the fusion of gametes.
- The two main pre-fertilisation events are gametogenesis and gamete transfer.
notes
A) Gametogenesis:
- Gametogenesis refers to the process of formation of the two types of gametes – male and female.
- Gametes are haploid cells. Gametes divide into two types -
a) Homogametes (isogametes): The two gametes are similar so it is not possible to classify them as male or as female gametes. Therefore, they are called homogametes (isogametes). For example - some algae like Cladophora.
Isogametes of Cladophora
(an alga)
Heterogametes of Fucus
(an alga)Heterogametes of Homo sapiens
(Human beings)
Sexuality in organisms:
- Sexual reproduction in organisms, in general, involves the fusion of gametes from two different individuals. But this is not always true.
- Bisexual: Both male and female reproductive structures are present in the same individual.
(i) Bisexual Plants and Fungi: Both male and female reproductive structures are present in the same plant. In several fungi and plants, terms such as homothallic and monoecious are used to denote the bisexual condition. In some flowering plants, both male and female flowers may be present on the same individual, it is called monoecious. Some examples of monoecious plants are cucurbits and coconuts.
Monoecious plant (Chara)
Bisexual flower (sweet potato)
Bisexual animal (Earthworm)
- Unisexual: Male and female reproductive structures are present in different individuals.
(i) Unisexual Plants and Fungi: Both male and female reproductive structures are present in the different plants, it is called unisexual plants. In several fungi and plants, Heterothallic and dioecious are the terms used to describe unisexual conditions. In flowering plants, the unisexual male flower is staminate, i.e., bearing stamens, while the female is pistillate or bearing pistils. In some flowering plants, both male and female flowers may be present on separate individuals, it is called dioecious. Some examples of dioecious plants are papaya and date palm.
Dioecious plant (Marchantia)
Unisexual animal (Cockroach)
Cell division during gamete formation:
-
A haploid parent produces gametes by mitotic division.
-
Several organisms belonging to monera, fungi, algae and bryophytes have haploid plant body, but for organisms belonging to pteridophytes, gymnosperms, angiosperms and most of the animals including human beings, the parental body is diploid. It is obvious that meiosis, the reduction division, has to occur if a diploid body has to produce haploid gametes.
-
In diploid organisms, specialized cells called meiocytes (gamete mother cells) undergo meiosis. At the end of meiosis, only one set of chromosomes gets incorporated into each gamete.
Chromosome Numbers in Meiocytes (diploid, 2n) and Gametes (haploid, n) of Some Organisms | ||
Plants | ||
Name of organism | Chromosome number in meiocyte (2n) | Chromosome number in gamete (n) |
Onion | 32 | 16 |
Potato | 48 | 24 |
Maize | 20 | 10 |
Rice | 24 | 12 |
Apple | 34 | 17 |
Ophioglossum (a fern) | 1260 | 630 |
Animals | ||
Human beings | 46 | 23 |
Housefly | 12 | 6 |
Rat | 42 | 21 |
Dog | 78 | 39 |
Cat | 38 | 19 |
Fruitfly | 8 | 4 |
Butterfly | 380 | 190 |
notes
(B) Gamete Transfer:
- Male gametes need a medium to move towards female gametes for fertilisation. In a majority of organisms, the male gamete is motile and the female gamete is stationary.
- Exceptions are a few fungi and algae in which both types of gametes are motile.
Homogametic contact in alga
- In several simple plants like algae, bryophytes and pteridophytes, water is the medium through which this gamete transfer takes place. A large number of the male gametes, however, fail to reach the female gametes. To compensate for this loss of male gametes during transport, the number of male gametes produced is several thousand times the number of female gametes produced.
-
In seed plants, pollen grains are the carriers of male gametes and the ovule has the egg. Pollen grains produced in anthers have to be transferred to the stigma before it can lead to fertilisation.
-
In bisexual, self-fertilizing plants, e.g., peas, transfer of pollen grains to the stigma is relatively easy as anthers and stigma are located close to each other. Pollen grains soon after they are shed, come in contact with the stigma. But in cross-pollinating plants (including dioecious plants), pollination facilitates the transfer of pollen grains to the stigma. Pollen grains germinate on the stigma and the pollen tubes carrying the male gametes reach the ovule and discharge male gametes near the egg.
- In dioecious animals, since male and female gametes are formed in different individuals, the organism must evolve a special mechanism for gamete transfer. Successful transfer and coming together of gametes is essential for the most critical event in sexual reproduction, the fertilisation.
If you would like to contribute notes or other learning material, please submit them using the button below.
Shaalaa.com | Sexual Reproduction: Juvenile Reproduction
to track your progress
Related QuestionsVIEW ALL [31]
Related concepts
Advertisement Remove all ads