Presentation on theme: "2.2 Sexual Reproduction in Animals"— Presentation transcript:
12.2 Sexual Reproduction in Animals Sperm(23) zygote (46) embryo (46) Egg(23) adultAn embryo is a fertilized egg during early development.
2Successful sexual reproduction requires: both male and female gametes must arrive in the same place at the same time for fertilization.The zygote must receive adequate food, moisture, warmth, and protection to develop.
3Mating in the Animal Kingdom mating is timed for offspring to be born at times with the best chance for survivalelk, deer, etc. once a yeargrunion mate at full or new moon.Honeybee’s mate once in a lifetimeDesert Toads only after a rainfall.
4FertilizationIn a warm, moist environment ONLY for sperm to swim, and for fertilization to result.May be INTERNAL or EXTERNAL.
5External Fertilization Most water-dwelling animals.Non-moving animals - (ex. Anemones) release large numbers of eggs and sperm into water. Eggs and sperm meet by chance. Zygotes form larvae which swim and feed themselves.Swimming animals – (fish) Females lay eggs in suitable spot. Males release sperm onto the egg cluster. This is called spawning.Sockeye Salmon Video -- National Geographic
6Internal Fertilization Animals on land (& aquatic mammals) use this method.Sperm is transferred directly to the female.
7ReptilesMale transfers sperm into female’s cloaca (where urinary, reproductive and digestive ducts lead).Eggs have enough food to feed the embryo until hatching.No care for young.
13The cost of reproduction The male empid fly offers his larger partner the gift of a smaller insect to avoid being eaten after mating.The male praying mantis shows up empty handed and the larger female often eats the smaller male after mating (starting with the head).
14Mammals Internal fertilization embryo develops inside mother for protection and nourishment (Placenta and umbilical cord)mother produces milk and parents care for young.
15Marsupials Kangaroos, Opossums give birth very early in development Young must crawl into pouch and attach to a nipple for food for several months while they develop.
16HermaphroditesHave both male and female reproductive organs on each individual.Includes flatworms (planaria), and earthworms.Each hermaphrodite injects sperm into the other’s reproductive pore.
17Assignment HowStuffWorks Videos "Fertilization and Sexual Reproduction: Part I"Questions on page 59 # 1 – 7Sexual Reproduction Handout (Manitoba Fisheries)“Fish Net” Scavenger Hunt – Group Activity
18PageThe fundamental cycle that allows all animals to reproduce sexually is:Meiosis produces gametesFertilization (male gamete combines with female gamete)Zygote produced embryoEmbryo develops through mitosis into mature offspring – cycle repeats
19Sexual Reproduction Questions FertilizationExternal fertilization takes place outside the organisms bodyInternal fertilization sperm are transported into the oviducts of the femaleAmphibians and most fish use external fertilization
20The disadvantages of external fertilization are: Only one parent to care for offspringParent usually disappears – no care for eggsLess genetic variability in organisms of same speciesInternal fertilization is necessary because there is no aquatic environment and fewer eggs are produced (therefore more parental care is provided)
21The purpose of the amniotic egg is to provide a “life raft” for water animals The chicken’s egg white provides an artificial pond for the developing embryoAmniotic egg must be fertilized internally so that the sperm can enter the egg before the shell formsA placental mammal is an animal that keeps the embryo inside their bodies in a specialized area called the womb/uterus.
22Care for young because they have fewer to ensure survival. All embryos develop in a “pond.” The embryo develops in a bag filled with amniotic fluid – this breaks just before birth.