1. Reproductive Patterns Sexual vs. Asexual Internal and External Fertilization and development

2. Types of Reproduction  There are two main types of reproduction: sexual and asexual.

3. Asexual reproduction:  The process by which offspring are formed WITHOUT the FUSION of an egg and sperm.  Only ONE individual is involved in the process.  There are many different forms such as: BUDDING, BINARY FISSION and FRAGMENTATION.  Organisms that reproduce asexually do NOT have a gender or sex organs.  For example: There are NOT male and female bacteria….just bacteria.

4. Asexual reproduction has several advantages: 1. SESSILE animals (animals that CANNOT move) can reproduce without finding a mate. 2. Allows the production of MANY offspring in a short period of time because all individuals in a population reproduce.

5. Drawback of asexual reproduction:  All of the offspring are CLONES (identical in DNA), so if conditions change and they are no longer well adapted to their environment, there is a good chance that all or most will die.

6. Types of Asexual Reproduction: Budding: occurs when a new individual develops on the SIDE of the parent. The OFFSPRING may stay attached or FALL off to begin an independent life.

7. Types of Asexual Reproduction: -Binary Fission: involves the separation of a parent into TWO or more individuals of approximately the same SIZE.

8. Types of Asexual Reproduction: Fragmentation or Regeneration:  the SPLITTING apart of an organism into several pieces.  Each piece re-grows (regenerates) the missing parts and develops into a new INDIVIDUAL.

10. Starfish Regeneration

11. Sexual reproduction:  The process by which offspring are formed by the fusion of egg and sperm to form a diploid (contains TWO copies of each chromosome) ZYGOTE.  FERTILIZATION = fusion of egg and sperm  Offspring receive HALF of their DNA from each parent.  Offspring are GENETICALLY DIVERSE>  This type of reproduction increases the genetic diversity of the species. It is ADVANTAGEOUS in environments that are under constant stress.

12. Drawbacks of sexual reproduction:  Have to find a PARTNER  Have to wait until sexual MATURITY  Not all members of the population REPRODUCE

13. Major Mechanisms of Fertilization: External Fertilization:  Eggs are shed into the ENVIRONMENT and fertilized by the male.  Occurs in moist habitats where development can occur without the fear of DRYING OUT.  The process can occur without CONTACT between the parents.  Chemical signals coordinate the process insuring the gametes are not WASTED.

14. Major Mechanisms of Fertilization: Internal Fertilization:  Occurs when sperm are deposited in or near the FEMALE reproductive tract and fertilization occurs INSIDE the female body.  Requires a more SOPHISTICATED reproductive system and cooperative mating behaviors.

15. Embryo Development  Embryos can develop INTERNALLY or EXTERNALLY.  Internal development means that the embryos develop INSIDE the body of the mother.  In order for internal development to occur, there had to have been INTERNAL fertilization.  Animals that follow this development pattern are referred to as having “ LIVE YOUNG ”.  Embryos may also develop externally, or OUTSIDE the body of the mother.  External development may happen after either INTERNAL or EXTERNAL fertilization.

16. Embryo Protection  Externally produced embryos are protected in several ways: They may be covered with a JELLY LAYER which allows for free gas exchange with the environment and provide the embryo with moisture. LARGE numbers of zygotes are produced to insure that some reach maturity. (100 ’ s, 1,000 ’ s, maybe even millions)

17. Internally produced embryos:  May be protected by an egg shell, as in reptiles and birds.  Some are LEATHERY and some are HARD.  PLACENTAL mammals retain their offspring in a special structure called the uterus.  Internally protected zygotes have a HIGHER rate of survival, and therefore, less ZYGOTES are produced.