Plant and Animal | Growth and Reproduction

• Some plants have determinate growth which means they stop growing
• Others continue growing by adding nodule after nodule. This is called indeterminate growth which persists as long as environmental conditions allow it.
• Most animals, in contrast, are characterized by determinate growth which means that they cease growing after reaching a certain size.
• Plant growth occurs in the meristems, regions that undergo mitotic division. A meristem consists of cells that divide frequently, thus adding new cells.
• Three main parts of the meristems are

  • Apical
  • Intercalary
  • Lateral
• These are two types of growth that occur in plants

  • Primary Growth
  • Secondary Growth
• Primary growth lengthens the root or shoot tip by adding cells produced by the apical meristems
• Secondary growth is the result of increase in girth of woody plants
• This is an increase in thickness of stems and secondary growth of roots caused by the activity of two cylinders of dividing cells called lateral meristems
• Chemicals called hormones regulate many aspects of plant growth, flower and fruit development, senescence and responses to environmental changes. A hormone is a biochemical synthesized in small quantities in one part of the organism and transported to another location where it stimulates or inhibits a response from target cells.
• The "Classic Five" Plant Hormones

  • Abscisic Acid
  • Auxin
  • Cytokinin
  • Ethylene
  • Gibberellin
• Growth in animals is more restricted in time and cell division is more generally distributed throughout the body of the organism.
• The rates of growth and cell division can vary widely in different body parts defining the shape of an organism
• The body naturally produces growth hormone (GH) in the pituitary gland, which is responsible for cell growth and regeneration.
• Growth hormone also plays a major role in maintaining the health of all human tissue, including that of the brain and other vital organs.
• Reproduction is the biological process by which new individual organisms - "offsprings" - are reproduced from their parents
• Reproduction is a fundamental feature of all known life; each individual organism exits as a result of reproduction.
• Plants have reproductive structures called flowers.
• Plants reproduce sexually through pollination
• Pollination refers to the transfer of pollen from the anther to the stigma of the same flower or another flower
• Self-pollination is when the pollen from one flower is transferred to the stigma of another flower
• Cross-pollination is the transfer of pollen from one flower to another of the same species
• The two main types of asexual reproduction in plants are vegetative propagation and apomixis
• Vegetative propagation means that the plant grows from a piece of the parent plant, such as a cutting or a shoot
• Some plants can reproduce seeds without fertilization. Either the ovule or part of the ovary which is diploid in nature, gives rise to a new seed. This type of asexual reproduction is known as apomixis.
• Sexual reproduction in animals is the production of genetically unique offspring by the union of sperm and egg nuclei to form a zygote.
• This union of male gamete and female gamete is called fertilization.
• Viviparous: (of an animal) bringing forth live young which have developed inside the body of the parent.
• Oviparous: (of an animal) producing young by means of eggs which are hatched after they have been laid by the parent, as in birds.
• Ovoviviparous: (of an animal) producing young by means of eggs which are hatched within the body of the parent, as in some snakes.
• Asexual reproduction is when one parent produces offspring with the same genetic makeup as itself
• Abscisic Acid inhibits shoot growth and maintains bud dormancy
• Auxin stimulates elongation of cells in stem
• Auxin controls phototropisms, gravitropism, thigmotropism
• Cytokinin stimulates cell division in seeds, roots, young leaves, fruits
• Ethylene hastens fruit ripening
• Ethylene participates in thigmotropism
• Gibberellin simulates cell division and elongation in roots, shoots, young leaves