The Continuity of Life Reproduction Sexual Reproduction Asexual

The Continuity of Life Reproduction Sexual Reproduction Asexual Reproduction

SEXUAL REPRODUCTION In sexual reproduction, genetic information from two cells combines to produce a new organism. Usually, two specialized sex cells unite in sexual reproduction and they form a fertilized egg called a ZYGOTE. Zygote contains a mixture of the two parent organisms genetics.

Sexual reproduction advantages • Genetic variation • Offspring are dispersed widely to end up in different places from their parents. Sexual reproduction disadvantages • Need two parents “must expend energy” to find, identify (court), and copulate with mate • Only half the individuals are producing offspring(Males are an energy issue) • Less efficient at passing on genes as their may be mistakes in the copying process of DNA

Types of Sexual Reproduction Hermaphrodism: both sexes occur in the same organism Some self-fertilize, others, cross-fertilize These organisms have both male and female reproductive organs, and are said to be monoecious, meaning “one house. ” Almost 70% of plants! And earthworms. .

Types of Sexual Reproduction Sequential Hermaphrodism or Sex switching: individual changes sex during life. Usually male and then female. Reversal often associated with weight and size Female Male

: t a k o o l s ’ t Le Asexual Reproduction

ASEXUAL REPRODUCTION

Asexual disadvantages No recombination of genes An asexual population tends to be genetically static Asexual advantages Need one individual to reproduce; can conserve energy No genetic change “good” if environment is stable All individuals are producing offspring More efficient passing genes, “faster”

Definition Sexual Reproduction Asexual Reproduction • Involves sex cells and fertilisation • Does not involve sex cells and fertilisation • Only one parent plant Advantages/ Disadvantages • Offspring are not genetically identical to one another • There is variation in the offspring • Offspring have no variation • Offspring are genetically identical to one another

Sexual vs. Asexual Some organisms are capable of both sexual & asexual Øcommon in plant kingdom!! WHY? ? ? Asexual • produces identical copy (clone) relatively fast • Easiest means of reproduction Sexual • requires more energy & time than asexual • produces genetic variation

Sexual vs. Asexual When environment is not changing… Asexual will allow well-adapted organisms to rapidly reproduce When environment is ever changing… Asexual will have difficulty adapting Sexual allows species shows variance between generations, which will have a better chance of survival

Imagine… Imagine that a particular organism within a species lacks a certain gene (or ability to express a certain gene) necessary to break down a specific type of food, yet others of the same species within the population are able to break down that food. What happens if the uncertain or less favorable conditions lead to that being the primary food source?

Death… The parent organism and all of their offspring produced would die! But, with the genetic diversity that comes from sexual reproduction the possibility of the offspring surviving is enhanced.

Activity

Methods of asexual reproduction Binary Fission – ex. Amoeba Budding – ex. yeast Fragmentation – ex. Sea Star Vegetative Propagation – ex. Kalanchoe Spores – ex. Ferns

Types of Asexual Reproduction Unicellular: Fissionsplitting into two organisms from one

BINARY FISSION An organism simply splits into equal sized offspring. + Fast and easy - Everybody has the same DNA

Budding… New Organisms Arise as an Outgrowth from the Parent Organism Seen Mostly in Marine Animals Examples Include; Sponges, Corals and Jellyfish… Coral Polyp Photo courtesy Jeffrey N. Jeffords http: //oceanworld. tamu. edu/students/coral 1. htm

They Where best buds Budding = Parent organism divides into two unequal parts. The new organism is created as a smaller out growth or bud on the outside of the parent. Buds will brake off and live independently or remain attached and form a colony.

BUDDING The offspring begins as a small outgrowth from the parent and eventually breaks off. Yeast & hydras + Fast, somewhat easy - Same DNA

Regeneration… This refers to the ability of some animals to re-grow severed parts. Some of these animals can also grow new organisms from the severed pieces (Segmented Worms and Sea

Don’t try this at home Regeneration = The ability to re-grow lost or damaged body parts. Hydra, planaria, starfish, and earthworm More complex animals less able to re-grow parts. Crab can re-grow a claw. Some reptiles can re-grow a tail. Most mammals can repair damaged tissue but can not re-grow missing parts.

FRAGMENTATION A new organism forms from a part that breaks off from the parent. Fungi & sea stars + Easy - Parent broken, same DNA

FRAGMENTATION Moss

Parthenogenesis… Offspring can arise from unfertilized eggs. Includes some Fish, Reptiles, Amphibians and Aphids. Most of these species can switch between Sexual and Asexual Reproduction. (depending on conditions) http: //aolsearch. aol. com/aol/image. Details? in vocation. Type=image. Results&query=photos +of+parthenogenic+species&img http: //spot. colorado. edu/~noyesr/TEACHING/4 800%20 Fall%202002. %20 Biology%20 and%2 0 Evolution%20 of%20 Sex/Gynogenesis. Poecili a. pdf http: //www. duke. edu/%7 Ejsr 6/ Hawaiipics/Rhampho. jpg www. ag. ndsu. nodak. edu

VIDEO CLIPS http: //www. youtube. com/watch? v=K 0 ZP 8 Vtx. UZ 0 (Binary Fission) http: //www. youtube. com/watch? v=l 7 JYv. XPRPl. E (Binary Fission) http: //www. youtube. com/watch? v=dc. NEf. Un. Et_g (Budding)