1. Lesson Overview Lesson OverviewReproduction Lesson Overview 28.3 Reproduction

2. Lesson Overview Lesson OverviewReproduction Asexual Reproduction Asexual reproduction requires only one parent, so individuals in favorable environmental conditions can reproduce rapidly. Carry only a single parent’s DNA, they have less genetic diversity than do offspring produced sexually. Lack of genetic diversity can be a disadvantage to a population if its environment changes.

3. Lesson Overview Lesson OverviewReproduction Asexual Reproduction Animals reproduce asexually in many ways. Some cnidarians divide in two. Budding produces new individuals as outgrowths of the body wall. Parthenogenesis-produces offspring that carry DNA inherited only from their mothers. Ex.) Females of some species can reproduce asexually by producing eggs that develop without being fertilized.

4. Lesson Overview Lesson OverviewReproduction Sexual Reproduction Sexual reproduction involves 2 species genetically diversity is an advantage When gametes (sperm and egg) join during fertilization- producing a zygote. Sexual reproduction maintains genetic diversity in a population-new combinations of genes. Genetic diversity is the raw material on which evolution operates. Sexually reproducing populations are better able to adapt to changing environmental conditions. Sexual reproduction requires 2 individuals of different sexes, so the density of a population must be high enough to allow mates to find each other.

5. Lesson Overview Lesson OverviewReproduction Sexual Reproduction In most animal species that reproduce sexually, each individual is either male or female. Among annelids, mollusks, & fishes, some species are hermaphrodites, which means that some individuals can be both male and female or can convert from one sex to the other. Clownfish, may change from one sex to the other as they mature.

6. Lesson Overview Lesson OverviewReproduction Reproductive Cycles A number of invertebrates have life cycles that alternate between sexual and asexual reproduction. Parasitic worms & cnidarians alternate between forms that reproduce sexually and forms that reproduce asexually.

7. Lesson Overview Lesson OverviewReproduction Reproductive Cycles Many cnidarians alternate between two body forms: polyps &medusas that swim freely in the water. Life cycle of the jellyfish: polyps produce medusas asexually by budding. The medusas reproduce sexually- eggs & sperm that are released into the water. After fertilization, the zygote grows into a free-swimming larva The larva eventually attaches to a hard surface & develops into a polyp continuing the cycle.

8. Lesson Overview Lesson OverviewReproduction Asexual and Sexual Reproduction How do asexual and sexual reproduction in animals compare?

9. Lesson Overview Lesson OverviewReproduction Asexual and Sexual Reproduction How do asexual and sexual reproduction in animals compare? Asexual reproduction requires only one parent, so individuals in favorable environmental conditions can reproduce rapidly. But since offspring produced asexually carry only a single parent’s DNA, they have less genetic diversity than do offspring produced sexually. Sexual reproduction maintains genetic diversity in a population by creating individuals with new combinations of genes.