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DO NOW: Is reproduction necessary?. Fertilization. The joining of male and female reproductive cells (sperm and egg cells). Crossing Over. Exchange of genes (alleles) between pairs of chromosomes. Independent Assortment.
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Fertilization The joining of male and female reproductive cells (sperm and egg cells)
Crossing Over Exchange of genes (alleles) between pairs of chromosomes
Independent Assortment When genes are exchanged, it is totally up to chance! Each gamete has more than 6 million possible combinations of mother and father’s chromosomes!
Mutations “Mistakes” in matching. Could introduce a new gene into a population.
Nondisjunction Chromosomes do not separate during cell division. The wrong number of chromosomes end up in a sex cell (gamete), which can cause BIG problems!
What is a species? • A species is a group of closely related organisms that share certain characteristics and can produce new individuals through reproduction
What if species couldn’t reproduce? • All individuals eventually die, but the species continues because individuals reproduce. Liger Cannot reproduce with another Liger
Survival • For a species to survive past a single generation, reproduction is essential. • The continuity (survival) of a species depends on reproduction. Without reproduction, all the organisms of a species would eventually die.
Two Methods of Fertilization • There are two basic ways in which gametes are brought together: • internal fertilization and external fertilization. • During internal fertilization the gametes fuse inside the body • During external fertilization the gametes fuse outside the body of the female.
What do you think offers more protection for the zygote, internal fertilization or an external fertilization? Why?
What animals use internal fertilization? • Vertebrates that reproduce on land and some aquatic mammals. • What animals use external fertilization? • Most aquatic animals and almost all plants.
VIVA = live viparous = birth • O / OVO = egg • TURN & TALK: Based on the prefixes above what do you think these words mean? • Viviparous • Oviparous • Ovoviviparous
VIVA = live viparous = birth O / OVO = egg Species that are: Viviparous = live birth organisms including most mammals where the young develop inside the female reproductive system and are birthed live. Oviparous Ovoviviparous
VIVA = live viparous = birth O / OVO = egg Species that are: Viviparous Oviparous= hatched from an egg organisms include most insects, reptiles, and all birds. Eggs continue to develop after being laid. Ovoviviparous
VIVA = live viparous = birth O / OVO = egg Species that are: Viviparous Oviparous Ovoviviparous = egg hatches during birth, appears to be a live birth organisms like the garden snake or Madagascar hissing cockroaches that have eggs that hatch as they are laid making it look like live birth.