Reproduction The Continuity of Life Reproduction Sexual Asexual

gametes TWO parents

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 disadvantages 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

Let’s look at: Asexual Reproduction

ASEXUAL REPRODUCTION In asexual reproduction, a single organism gives rise to offspring with identical genetic information. Asexual reproduction = one parent. The offspring is an exact copy of the parent = clone!

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”

Sexual Reproduction Asexual Reproduction Definition Advantages/ 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 common 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.

Binary Fission Fragmentation Activity Parthenogenesis Budding

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:  Fission-splitting 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/coral1.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 Stars)

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 or Clonal Fragmentation is a form of asexual reproduction or cloning where an organism is split into fragments. The splitting may or may not be intentional. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. If the organism is split any further the process is repeated. Fragmentation is seen in many organisms such as molds, some annelid worms, and starfish. Binary fission of single-celled organisms such bacteria, protozoa and many algae is a type of fragmentation. Molds, yeast, and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues. Fragmentation is observed in nonvascular plants as well, liverworts and mosses.

FRAGMENTATION Fragmentation or Clonal Fragmentation is a form of asexual reproduction or cloning where an organism is split into fragments. The splitting may or may not be intentional. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. If the organism is split any further the process is repeated. Fragmentation is seen in many organisms such as molds, some annelid worms, and starfish. Binary fission of single-celled organisms such bacteria, protozoa and many algae is a type of fragmentation. Molds, yeast, and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues. Fragmentation is observed in nonvascular plants as well, liverworts and mosses. 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/imageDetails?invocationType=imageResults&query=photos+of+parthenogenic+species&img http://www.duke.edu/%7Ejsr6/Hawaiipics/Rhampho.jpg http://spot.colorado.edu/~noyesr/TEACHING/4800%20Fall%202002.%20Biology%20and%20Evolution%20of%20Sex/Gynogenesis.Poecilia.pdf www.ag.ndsu.nodak.edu

VIDEO CLIPS http://www.youtube.com/watch?v=K0ZP8VtxUZ0 (Binary Fission) http://www.youtube.com/watch?v=l7JYvXPRPlE (Binary Fission) http://www.youtube.com/watch?v=dcNEfUnEt_g (Budding)