Biology
Class Notes
Lesson 12 Reproduction
Objective: 2.1.2
Species: A group of similar organisms that can breed and
produce viable fertile offspring.
*Without successful reproduction, a species will cease to
exist.
Asexual Reproduction: The formation of offspring from a
single parent.
 Offspring are genetically identical to the parent.
 Mitosis, which is use for cell replacement by multicellular
organism, is used by unicellular eukaryotes such as protists
to reproduce.
 Prokaryotes (bacteria and archaea) reproduce asexually by
binary fission.
http://www.youtube.com/watch?v=_FBBnNhN_NM&featu
re=related,
http://www.youtube.com/watch?v=SLpFJ1JeRYs
 Hydras (tube shaped freshwater animal related to jellyfish)
and yeast fungi reproduce asexually by budding.
http://www.youtube.com/watch?v=489CSop00sY
 Some species of sponges, worms and sea stars can
reproduce asexually by fragmentation.
http://www.youtube.com/watch?v=f7cXeWxxfD4
 Plants reproduce asexually by sprouting new plants from
roots or cutting.
Sexual Reproduction: When two parent sex cells join together
to form a new individual.
 Typically, male and female gametes join by fertilization.
 Earthworms are hermaphroditic, but cannot fertilize
themselves.
 Monecious plants can fertilize themselves.
Sexual Reproduction of Plants
Ferns
Spore: A single reproductive fern cell that can grow to
become a new plant.
Sporophyte: A plant structure that makes spores.
Gametes: Sex cells (i.e. male sperm and female egg).
Gametophyte: A plant structure that makes gametes.
Zygote: A fertilized egg.
1. A spore lands in a suitable place and becomes a prothallus.
2. The prothallus produces gametes.
3. The male gamete fertilizes the female gamete.
4. A new fern develops into a mature fern.
5. More spores are produced.
Angiosperms (flowering Plants)
Embryo: An unborn, unhatched or dormant offspring in the
process of developing.
Seed: A reproductive plant structure that contains a plant
embryo.
1. Pollen lands on the stigma and goes down the style to the
ovary.
2. The egg in the ovary is fertilized and becomes a zygote
3. The embryo develops into a seed and is typically
surrounded by a fruit.
4. The fruit lands in a new location and the seed sprouts to
become a new plant.
5. The new plant forms flowers and the process is repeated.
Gymnosperms (nonflowering plants)
1. Male cones produce pollen.
2. Female cones produce ovules, which contain egg cells.
3. Pollen lands on a female cone and fertilization occurs.
4. Cones expand to release the seeds, which are dispersed.
5. Seeds sprout to become new plants, which produce more
male and female cones.
Sexual Reproduction in Animals
While a few animals such as hydras and drone bees (i.e.
unfertilized) are reproduced asexually, most animals
reproduce sexually.
External Fertilization: Fertilized outside the female body.
 Sperm cells must be released into a fluid environment.
 Timing is controlled by the release of hormones to signal
readiness.
 As the female begins to lay eggs, the male receives a signal
and deposits sperm.
Ex: Most fish and many amphibians
Internal Fertilization: Fertilized inside the female body.
 May lead to live birth or the laying of a fertilized egg.
Ex: Insects, reptiles, birds, mammals and a few aquatic
animals such as sharks, aquatic mammals, and
lobsters.
Live Birth in Mammals
 All mammals reproduce sexually using internal
fertilization.
Mammal Groups
Marsupials: Mammals that develop for a short time inside
the mother’s body and then develop further in a
protective pouch while attached to a nipple.
Ex: Most are in Australia and include koalas,
kangaroo.
Ex: The only N. American marsupial is the opossum.
Placental Mammals: Mammals that give birth to live
young that have developed inside an organ in the
mother’s body called a uterus.
Placenta: An organ in pregnant females that passes
nutrients oxygen to the developing embryo and carries
waste away through the umbilical cord.
Monotremes: Mammals they lay eggs.
Ex: Echidna and duck-billed platypus.
Reproduction in Fungi
Fungi: A diverse group of unicellular and multicellular
organisms that include: yeasts, molds, mildews, mushrooms,
and bracket fungi.
 Can reproduce sexually by producing spores or asexually
by budding (e.g. yeasts).
Pros and Cons of Asexual and Sexual Reproduction
Asexual
Pros
 Only requires one parent.
 Is a fast way to produce many offspring.
 Does not require courtship or even finding a mate.
Cons
 Leads to low genetic diversity and vulnerability to disease,
environmental change, etc. Evolution occurs primarily
through mutation.
Sexual
Pros
 Leads to more genetic diversity and overall fitness.
Evolution occurs through mutation, natural selection and
random genetic drift.
Cons
 It is slower.
Key Words:
Species
Asexual reproduction
Sexual reproduction
Spore
Seed
External fertilization
Internal fertilization
Marsupial
Placental mammal
Placenta