BIOLOGY 3201 REPRODUCTION Asexual vs. Sexual Reproduction MODES OF REPRODUCTION (1) Asexual one parent cell divides into two by mitosis to produce 2 identical cells which are clones of the parent (2) Sexual new offspring are created as a result of the fusion of an egg and sperm. The offspring resemble but are not identical to the parents 1
ASEXUAL REPRODUCTION Asexual reproduction can be advantageous when animals remain in one particular place Asexual reproduction results in numerous offspring that can be produced without "costing" the parent a great amount of energy Asexual reproduction is good where environments that are stable TYPES OF ASEXUAL REPRODUCTION 2
1. BUDDING offspring develop as a growth on the body of the parent examples: cnidarians yeast 3
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2. FRAGMENTATION spontaneously break up into pieces. Each piece develops into a mature organism examples: flatworms, various fungi 5
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3. REGENERATION (FRAGMENTATION) dividing and re-growing missing parts. They also have the ability to regenerate injured body parts examples: some invertebrates such as Echinoderms (starfish), Planaria Planaria 7
4. BINARY FISSION parent cell splits in half producing two identical cells most unicellular organisms 8
5. PARTHENOGENESIS "virgin birth" females produce eggs, but these develop into young without ever being fertilized. some fishes, several kinds of insects, and a few species of lizards 9
IN HONEYBEES. fertilized eggs (diploid) become females; unfertilized (haploid) eggs become males The queen controls the sex of her offspring. When an egg passes from her ovary to her oviduct, the queen determines whether the egg is fertilized with sperm from the spermatheca. A fertilized egg develops into a female honey bee, either worker or queen, and an unfertilized egg becomes a male honey bee, or drone. BIOLOGY 3201 UNIT 2: REPRODUCTION Seed Plants 10
PLANT REPRODUCTION Plants experience two distinct generations during their life cycle Sporophyte generation produces spores (asexual by mitosis) Gametophyte generation produces gametes (sexual by meiosis) However, angiosperms (flowering plants) do not use any asexual reproduction; the sporophyte generation doesn t produce spores at all. As well, the gametophyte generation is reduced to pollen grains and ovum cells SEED PLANTS Most abundant Sporophyte generation predominant gametophyte gen reduced to sex cells Reproductive organs - flowers 11
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FLOWERS Diploid Perfect - both male and female sex organs Imperfect - male or female flower FLOWERS CON T Pistil/Carpel - female Stamen - male 13
FLOWERING STRUCTURES IN ANGIOSPERMS: (1) pistil a carpel or a group of fused carpels forming the female reproductive part of a flower and including the ovary, style, and stigma ovary swollen base of the carpel that contains ovules style stalk that connects the stigma to the ovary stigma sticky lip of the carpel that captures pollen grains 14
FLOWERING STRUCTURES IN ANGIOSPERMS: (2) stamen pollen-producing reproductive organ of a flower, consisting of a filament and an anther filament the stalk which supports the anther anther top part of the stamen; produces pollen (3) pollen fine powdery material consisting of pollen grains (microspores of seed plants, containing male gametophytes) produced by anthers. It is carried by wind and insects to other flowers which it fertilizes. FLOWERING STRUCTURES IN ANGIOSPERMS: (4) ovules tiny structures in a seed plant, containing the embryonic sac and surrounded by the nucellus that develop into seeds after fertilization (5) seed reproductive structure of plants made up of an embryo, stored food (endosperm) and a tough waterproof coat (6) fruit structure formed by the ovary tissue of a flower 15
POLLEN PRODUCTION 1. Diploid cells in the anther undergo meiosis to produce 4 monoploid microspores. 2. Each monoploid nucleus divides by mitosis to produce 2 monoploid nuclei - the tube nucleus and the generative nucleus. 3. The outer wall of the microspore hardens forming a 16
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PRODUCTI ON 1. In the ovules diploid cells undergo meiosis to produce 4 monoploid cells on which only one survives. The surviving cell is the megaspore. 2. Megaspore divides 3 times by mitosis to form 8 nuclei - two are polar nuclei, one is the true egg, and five die. 18
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FERTILIZATION IN FLOWERING PLANTS 1. 2. 3. Pollen sticks to the stigma A pollen tube forms from the tube nucleus. Pollen tube enters the ovule through the micropyle. 20
4. Generative nucleus divides by mitosis to form two sperm nuclei 5. Sperm nuclei enter the ovule. 6. One sperm - joins 2 polar nuclei form the triploid (3n) endosperm 7. One sperm - joins the egg - fertilization producing a diploid zygote. 21
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FLOWERING PLANTS Fruit and Seed Formation STEPS... 1. Endosperm nucleus divides to become the endosperm. 2. 3. Out covering of ovule hardens into the seed coat. Ovary enlarges to become the fruit. 24
Strawberry Flower Developing Fruit 25