BIOLOGY LESSON 1 - 3

• Flower

  The reproductive shoots of the angiosperm sporophyte, are typically composed of four whorls of highly modified leaves called floral organs, which are separated by very short internodes.
• The floral organs – sepals, petals, stamens, and carpels (pistils) – are attached to a part of the stem called the receptacle.
• Stamens and carpels are reproductive organs, whereas sepals and petals are sterile.
• Sepals - which enclose and protect the floral bud before it opens, are usually green and more leaflike in appearance than the other floral organs
• Petals - are more brightly colored than sepals and attract the flower to insects and other pollinators.
• Stamen - consists of a stalk called the filament and a terminal structure called the anther
• Within the anther are chambers called pollen sacs, in which pollen is produced.
• Carpel - has an ovary at its base and a long, slender neck called the style.
• Types of flowers based on the presence of the whorls

  • Complete
  • Incomplete
• Complete - is a plant biology term that is used to describe a flower that is built with four parts which include the sepals, petals, pistils, and stamens.
• Incomplete - If any of the sepals, petals, pistils, and stamens, which are integral in forming a flower, is missing, a flower is called an incomplete flower.
• Types of flowers based on the presence of the reproductive whorls:

  • Perfect/Bisexual
  • Imperfect/Unisexual
• Perfect/Bisexual – is one in which both male and female reproductive structures are present.
• Androecium - whorl of stamens
• Gynoecium - whorl of carpels or pistil
• Imperfect/Unisexual - flower that does not have both male and female structures.
• Anthers and ovules bear sporangia, structures where spores are produced by meiosis and gametophytes develop.
• Pollination - is the transfer of pollen from an anther to a stigma.
• DOUBLE FERTILIZATION - After landing on a receptive stigma, a pollen grain absorbs moisture and germinates; that is, it produces a pollen tube that extends down between the cells of the style toward the ovary.
• From Ovule to Seed - After double fertilization, each ovule develops into a seed, and the ovary develops into a fruit enclosing the seed(s).
• From Ovary to Fruit - While the seeds are developing from ovules, the ovary of the flower is developing into a fruit, which protects the enclosed seeds and, when mature, aids in their dispersal by wind or animals.
• Label the diagram

  A) Simple Fruit

  B) Aggregate Fruit

  C) Multiple Fruit

  D) Accessory Fruit

  
• Two types of animal reproduction

  • Sexual
  • Asexual
• Asexual reproduction - is the creation of new individuals whose genes all come from one parent without the fusion of egg and sperm.
• Sexual reproduction - is the creation of offspring by the fusion of haploid gametes to form a zygote (fertilized egg), which is diploid.
• Female gamete - the unfertilized egg (also called an ovum), is a relatively large cell and not motile.
• Male gamete - the sperm, is generally a much smaller, motile cell.
• Sexual reproduction - increases genetic variability among offspring by generating unique combinations of genes inherited from two parents.
• Asexual reproduction - it enables animals living in isolation to produce offspring without locating mates.
• Sexual reproduction - may enhance the reproductive success of parents when environmntal factors (including pathogens) change relatively rapidly.
• Asexual reproduction - It can also create numerous offspring in a short amount of time, which is ideal for colonizing a habitat rapidly.
• Asexual reproduction - is most advantageous in stable, favorable environments because it perpetuates successful genotypes precisely.
• Types of Asexual Reproduction

  • Fission
  • Budding
  • Regeneration
  • Fragmentation
• Fission - the separation of a parent into two or more individuals of approximately equal size
• Budding - in which new individuals arise from outgrowths of existing ones
• Fragmentation - the breaking of the body into several pieces, some or all of which develop into complete adults.
• Regeneration - the regrowth of lost body parts; usually accompanied with fragmentation.
• Types of Fertilization

  • Internal Fertilization
  • External Fertilization
• Internal Fertilization - The male generally delivers sperm cells directly into the body of the female. Her moist tissues provide the watery medium required for movement of sperm.
• External Fertilization - Mating patners usually release eggs and sperms into the water simultaneously.