Maintaining the Continuity of Life

How is the continuity of life maintained? Through the processes of reproduction and development. Reproduction is necessary because all species have a finite lifespan.

To understand how the continuity of life is sustained it is important to understand how cells reproduce themselves.

The Process of Reproduction A life process by which living organisms produce other living organisms of the same species. Two Types: Sexual – requires 2 parents and produces offspring that are genetically different from both parents. Asexual – requires 1 parent and produces many offspring that are genetically identical.

Advantages and Disadvantages of Sexual Reproduction Advantages – Variety and/or diversity of offspring (color, shape, size, intelligence, ability, etc.), More able to adapt to environmental changes. Disadvantages – Uniqueness, sometimes traits needed for survival are not passed on.

Asexual Reproduction

Each new organism receives one full copy of DNA. Binary Fission - Organism duplicates its genetic material (DNA), then divides into two parts (cytokinesis). Each new organism receives one full copy of DNA. Diploid (100 % genetic material) Typically occurs in prokaryotes. Example: Bacteria

Regeneration - Development of a new organism from a part of the parent organism. Example: starfish, salamander

Budding – Organism that produces a bud that breaks away to live on its own. Example: Hydra, Yeast

Vegetative Propagation – Results in a new plant that is genetically identical to the parent plant (a clone). Examples: strawberry plant, vegetables, and crops.

Advantages and Disadvantages of Asexual Reproduction Advantages – Identical to parent, so will get all good characteristics. Disadvantages – Identical to parent, so will also get bad characteristics and is less able to adapt to the environment.

Reproduction Recap https://www.youtube.com/watch?v=jk2RJm5RBEk&list=PLVQzrzYgbDuwrv1ps4NJs0SBAOKxsn3Vf

STEPS OF MITOSIS (Asexual Reproduction) Produces clones of organisms

Mitosis Occurs in all body cells except sex cells. A complex series of changes in the nuclei of body cells that produce identical daughter cells with exactly the same number and type of chromosomes as the original cells called the parent cells. Also results in growth and repair of body tissues in multicellular organisms

The Phases of Mitosis Interphase: the resting phase, non-mitotic, during this time DNA is replicated. Homologous Chromosomes: A pair of chromosomes that have the same size, shape and genetic makeup

Prophase: Homologous chromosomes pair up and fasten to their centromeres. The nuclear membrane disappears and spindle fibers form. Pairs begin to migrate towards the equator

Metaphase Homologous chromosomes line up in the middle of the poles. Centromeres fasten to the spindle.

Anaphase Homologous chromosomes separate from each other and move to opposite ends of the cell.

Telophase Chromosomes condense Nuclear Envelope forms http://www.youtube.com/watch?v=ELVwj5JDfg8 Telophase Chromosomes condense Nuclear Envelope forms The cytoplasm divides forming 2 daughter cells Synchronized Swimming Mitosis Mitosis in a Winter Wonderland Mitosis Stages Song

When does cell division get out of control? Cells are exposed to mutagens (chemicals that cause mutations). If this happens, cell division may repeatedly occur. Uncontrolled cell division is called cancer.