Reproduction in Flowering Plants
Sexual Reproduction
- The process involving fusion of male and female gametes
- Occurs in the flowers of angiosperms
- Involves the transfer of pollen from the anther to the stigma
Advantages of Sexual Reproduction in Flowering Plants
- Genetic variation: offspring inherit traits from both parents
- Adaptability: helps plants survive in changing environments
- Development of new species: leads to evolution through genetic mutations
- Enhances genetic fitness
Disadvantages of Sexual Reproduction in Flowering Plants
- Dependence on external factors for pollination
- Competition for pollinators among flowers
- Decreased offspring production compared to asexual reproduction
- Requires specialized reproductive structures and mechanisms
Pollination: Transfer of Pollen
- Transfer of pollen grains from the anther to the stigma
- Can occur through self-pollination or cross-pollination
- Factors influencing pollination: wind, water, insects, birds
Self-Pollination
- Transfer of pollen from the anther of a flower to the stigma of the same flower, or a different flower on the same plant
- Reduces genetic variation
- Common in plants with closed flowers or in isolation
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Disadvantages of Cross-Pollination
- Requires the presence of pollinators to transfer pollen between flowers, increasing the reliance on external factors
- Competition for pollinators can lead to decreased chances of successful pollination
- Possibility of pollen wastage if it lands on the wrong stigma
- Genetic variation among offspring can lead to unpredictable traits
Fertilization in Flowering Plants
- The fusion of male and female gametes
- Occurs after the successful pollination and transfer of pollen
- Two main processes involved: pollen tube formation and double fertilization
- Pollen grain germinates on stigma and produces a pollen tube
- The tube grows through the style towards the ovary
- Nourishment for the growing pollen tube is provided by the style
Double Fertilization
- Involves the fertilization of two female gametes with two male gametes
- One male gamete fuses with the egg cell to form a zygote
- The other male gamete fuses with the two polar nuclei to form endosperm
- Results in the formation of both embryo and endosperm
Seed Development and Dispersal
- After fertilization, the ovule develops into a seed
- The seed consists of an embryo, endosperm, and seed coat
- Seed dispersal mechanisms: wind, water, animals, and self-dispersal mechanisms
- Allows for the distribution of plants in different habitats
Germination of Seeds
- Process by which a dormant seed starts to grow and develop
- Conditions required for germination: water, oxygen, suitable temperature
- Stages of germination: imbibition, activation of enzymes, growth of seedling
Asexual Reproduction in Plants
- Involves the production of offspring without the involvement of gametes
- Common methods of asexual reproduction in plants: vegetative propagation, budding, fragmentation, and spore formation
- Advantages of asexual reproduction: rapid population increase, offspring identical to parent
- Disadvantages of asexual reproduction: lack of genetic variation, vulnerability to environmental changes
Variations in a Population
- Variations can be inherited or caused by environmental factors
- Mutations, genetic recombination, and gene flow contribute to genetic variation
- Natural selection acts on variations, leading to better adaptation and evolution
- Population genetics studies the distribution of genetic variation within a population
Natural Selection and Evolution
- Process by which favorable traits are selected and passed on to the next generation
- Three main components of natural selection: variation, heredity, and differential reproductive success
- Types of natural selection: stabilizing selection, directional selection, disruptive selection
- Over time, natural selection can lead to the evolution of new species
Adaptations in Plants
- Adaptations help plants survive and reproduce in their environment
- Structural adaptations: specialized structures for specific functions (e.g., leaves, flowers, thorns)
- Physiological adaptations: biochemical or metabolic changes to cope with environmental conditions (e.g., drought tolerance)
- Behavioral adaptations: specific behaviors that increase survival and reproduction (e.g., seed dispersal)
- Adaptations can be inherited or acquired during an individual’s lifetime
Human Reproduction
- Human reproduction involves the production of gametes (sperm and egg)
- Male reproductive system: testes, epididymis, vas deferens, seminal vesicles, prostate gland, penis
- Female reproductive system: ovaries, fallopian tubes, uterus, cervix, vagina
- Fertilization occurs in the fallopian tubes, leading to embryo development in the uterus
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Disadvantages of Cross-Pollination
- Requires the presence of pollinators to transfer pollen between flowers, increasing the reliance on external factors
- Competition for pollinators can lead to decreased chances of successful pollination
- Possibility of pollen wastage if it lands on the wrong stigma
- Genetic variation among offspring can lead to unpredictable traits
Fertilization in Flowering Plants
- The fusion of male and female gametes
- Occurs after the successful pollination and transfer of pollen
- Two main processes involved: pollen tube formation and double fertilization
- Pollen grain germinates on stigma and produces a pollen tube
- The tube grows through the style towards the ovary
- Nourishment for the growing pollen tube is provided by the style
Double Fertilization
- Involves the fertilization of two female gametes with two male gametes
- One male gamete fuses with the egg cell to form a zygote
- The other male gamete fuses with the two polar nuclei to form endosperm
- Results in the formation of both embryo and endosperm
Seed Development and Dispersal
- After fertilization, the ovule develops into a seed
- The seed consists of an embryo, endosperm, and seed coat
- Seed dispersal mechanisms: wind, water, animals, and self-dispersal mechanisms
- Allows for the distribution of plants in different habitats
Germination of Seeds
- Process by which a dormant seed starts to grow and develop
- Conditions required for germination: water, oxygen, suitable temperature
- Stages of germination: imbibition, activation of enzymes, growth of seedling
Asexual Reproduction in Plants
- Involves the production of offspring without the involvement of gametes
- Common methods of asexual reproduction in plants: vegetative propagation, budding, fragmentation, and spore formation
- Advantages of asexual reproduction: rapid population increase, offspring identical to parent
- Disadvantages of asexual reproduction: lack of genetic variation, vulnerability to environmental changes
Variations in a Population
- Variations can be inherited or caused by environmental factors
- Mutations, genetic recombination, and gene flow contribute to genetic variation
- Natural selection acts on variations, leading to better adaptation and evolution
- Population genetics studies the distribution of genetic variation within a population
Natural Selection and Evolution
- Process by which favorable traits are selected and passed on to the next generation
- Three main components of natural selection: variation, heredity, and differential reproductive success
- Types of natural selection: stabilizing selection, directional selection, disruptive selection
- Over time, natural selection can lead to the evolution of new species
Adaptations in Plants
- Adaptations help plants survive and reproduce in their environment
- Structural adaptations: specialized structures for specific functions (e.g., leaves, flowers, thorns)
- Physiological adaptations: biochemical or metabolic changes to cope with environmental conditions (e.g., drought tolerance)
- Behavioral adaptations: specific behaviors that increase survival and reproduction (e.g., seed dispersal)
- Adaptations can be inherited or acquired during an individual’s lifetime
Human Reproduction
- Human reproduction involves the production of gametes (sperm and egg)
- Male reproductive system: testes, epididymis, vas deferens, seminal vesicles, prostate gland, penis
- Female reproductive system: ovaries, fallopian tubes, uterus, cervix, vagina
- Fertilization occurs in the fallopian tubes, leading to embryo development in the uterus