BIOLOGY

• Plant Reproduction


  Necessary for the survival and perpetuation of plant species that are such an important part of our daily lives. Plants have the capability to propagate or multiply themselves by means of sexual and/or asexual reproduction. Both methods of reproduction are important to the agricultural industry, specifically the commercial production of horticultural, agronomic, and forestry crops.
• Sexual Reproduction


  Seeds are the means by which plants sexually reproduce. They contain all the genetic characteristics of the parent plant. However, the characteristics of plants grown from seeds may vary from the parent plant. Seed propagation is the most economical and widely used method of producing new plants, provided that plants of the desired type can be reproduced by this method. Reproducing plants by seeds allows a grower to produce a large number of plants. Sexual plant reproduction involves reproducing plants from seeds. Seed formation occurs as a result of the pollination and fertilization processes that occur in the flowers of a plant. Stamens are the male reproductive part and pistil is the female reproductive part. Flowers which contain either only pistil or only stamens are called unisexual or dioecious flowers. Flowers which contain both stamens and pistil are called bisexual or monoecious flowers.

  
• Pollination


  1. Pollen grains come into contact with the moist, sticky surface of a stigma

  2. Self-pollination occurs when pollen comes into contact with a stigma within the same flower or other flowers on the same plant

  3. Flowers cross-pollinate when pollen from the flower of one plant transfers to stigmas of flowers on another plant

  
• Fertilization


  1. A pollen grain becomes anchored on the moist, sticky surface of the stigma, it germinates and produces a pollen tube

  2. The pollen tube grows down through the style and into the ovary where it eventually reaches an ovule

  3. Fertilization occurs when the male sex cell in the pollen tube unites with the female sex cell in the ovule

  4. One sperm cell from the pollen tube unites with the egg cell in the ovule to form a zygote

  5. The second sperm cell unites with two separate polar nuclei to form a primary endosperm nucleus
• Asexual Reproduction


  Involves the production of new plants by use of vegetative parts from an existing plant. Vegetative plant parts used in asexual reproduction include stems, buds, leaves, and roots. New plants are obtained without production of seeds. Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds.
• Budding


  1. A small bulb-like projection coming out from the yeast cell is called a bud

  2. The bud gradually grows and gets detached from the parent cell and forms a new yeast cell

  3. The new yeast cell grows, matures and produces more yeast cells

  4. Another bud arises from the bud forming a chain of buds
• Fragmentation


  1. An alga breaks up into two or more fragments

  2. These fragments or pieces grow into new individuals

  3. This process continues and they cover a large area in a short period of time
• Spore Formation


  1. Spores are asexual reproductive bodies

  2. Each spore is covered by a hard protective coat to withstand unfavorable conditions

  3. Under favorable conditions, a spore germinates and develops into a new individual

  4. Plants such as moss and ferns also reproduce by means of spores

  5. Myxomycetes or slime molds also release haploid spores
• Functions of the reproductive system

  • Provides process for reproduction
  • Production of offspring
• Types of Reproduction for Animals

  • Sexual reproduction
  • Asexual reproduction
• Male Reproductive Organs

  • Include a pair of testes, two sperm ducts and a penis
  • The testes produce the male gametes called sperms produced in the seminiferous tubules
  • Millions of sperms are produced by the testes
  • Each sperm has a head, a middle piece and a tail
• Female Reproductive Organs


  • Include a pair of ovaries, oviducts (fallopian tubes) and the uterus
  • The ovary produces female gametes called ova (eggs)
  • In human beings, a single matured egg is released into the oviduct by one of the ovaries every month
  • Uterus is the part where development of the baby takes place, and the vagina where sexual intercourse and passage of the offspring takes place
  • An egg is also a single cell

  
• Fertilization


  1. The fusion of a sperm and an ovum

  2. The nuclei of the sperm and the egg fuse to form a single nucleus, resulting in the formation of a fertilized egg or zygote

  3. Fertilization which takes place inside the female body is called internal fertilization

  4. Internal fertilization may result in the birth of either live offspring called viviparous or via eggs (oviparous) or ovoviviparous
• Modes of Reproduction and Fertilization in Animals


  • Viviparous: Producing young that have developed inside the body of their parent
  • Oviparous: Producing young by means of eggs that hatch after being laid by their parent
  • Ovoviviparous: Producing young by means of eggs that hatch within parent
  • Parthenogenesis: Producing an egg which later forms as an embryo without being fertilized
• External Fertilization

  1. As the eggs are laid, the male deposits sperms over them

  2. The sperms come in contact with the eggs, resulting in fertilization

  3. The fusion of a male and a female gamete takes place outside the body of the female
• Asexual Reproduction


  • Reproduction in which only a single parent is involved
  • New individuals develop from the buds in hydra, this type of asexual reproduction is called budding
  • An animal reproduces by dividing into two individuals
• Parthenogenesis


  Producing an egg which later forms as an embryo without being fertilized
• External fertilization


  1. Eggs are laid, the male deposits sperms over them

  2. Sperms swim randomly in water and come in contact with the eggs

  3. Fusion of a male and a female gamete takes place outside the body of the female
• Asexual reproduction

  Reproduction in which only a single parent is involved
• Asexual reproduction

  • Budding in hydra
  • Binary fission
  • Parthenogenesis in bees, aphids, and ants
• Plants can synthesize food for themselves but animals including humans cannot. They get it from plants or animals that eat plants.
• Autotrophic nutrition


  Mode of nutrition in which organisms make food themselves from simple substances
• Heterotrophic nutrition


  Mode of nutrition in which organisms take in food prepared by plants
• Heterotrophic nutrition

  • Parasitic plants like Cuscuta or Amarbel
  • Carnivorous plants like pitcher plant, venus fly-trap, and raflesia
  • Saprophytes like fungi and protists
• Plant nutrients

  • Macronutrients (Nitrogen, Phosphorus, Potassium)
  • Secondary nutrients (Calcium, Magnesium, Sulfur)
  • Micronutrients (Iron, Zinc, Manganese, Molybdenum, Copper, Boron, Chlorine)
• Gastrointestinal tract (GI tract)


  Continuous tube extending through the ventral cavity from the mouth to the anus
• Accessory structures of the digestive system

  Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
• Peristalsis


  Wavelike movement that occurs from the oropharynx to the rectum, allowing GI tract to push food particles toward the anus
• Mixing

  Mixing motion in the oral cavity and stomach that allows the GI tract to repeatedly break down food into smaller particles, using mechanical digestion
• Segmentation


  Regions of the small intestine contracting and relaxing independently, allowing the small intestine to digestive and absorb more efficiently
• Autonomic nervous system


  Parasympathetic nerves stimulate GI tract activities, sympathetic nerves inhibit GI tract activities
• Hormonal control

  Hormones from endocrine gland and from GI tract itself help regulate GI tract activities
• Reflex mechanism


  Regions of the GI tract (especially the stomach and small intestine) use reflexes to stimulate or inhibit one another
• Chemical digestion and absorption in the stomach

  1. Carbohydrate digestion continues with gastric amylase

  2. Protein digestion begins with pepsin

  3. Lipid digestion begins with gastric lipases

  4. Absorption in the stomach is limited, only small and fat-soluble substances can be absorbed