Sexual vs. Sexual vs. Asexual Asexual

ReproductionReproductionMitosis & MeiosisMitosis & Meiosis

Essential QuestionsEssential Questions

• What is the difference between sexual and What is the difference between sexual and asexual reproduction? (Mitosis & Meiosis)asexual reproduction? (Mitosis & Meiosis)

• What types of organisms produce What types of organisms produce sexually? Asexually?sexually? Asexually?

• What are the advantages and What are the advantages and disadvantages to each type of disadvantages to each type of reproduction?reproduction?

MitosisMitosis• Mitosis is used for:Mitosis is used for:

• Growth Growth • Cell ReplacementCell Replacement• RegenerationRegeneration• Asexual ReproductionAsexual Reproduction

MitosisMitosis• The process of mitosis occurs when a The process of mitosis occurs when a

cell cell copiescopies its its geneticgenetic information information onceonce and then and then divides oncedivides once. .

• For example: When human skin cell For example: When human skin cell undergo mitosis they start with undergo mitosis they start with 4646 chromosomes, those chromosomes chromosomes, those chromosomes make a copy of themselves, then the make a copy of themselves, then the cell divides, giving each of the new cell divides, giving each of the new cells a copy. cells a copy.

• The result is The result is twotwo identical cells with identical cells with 4646 chromosomes each. chromosomes each.

Some animals Some animals reproduce by reproduce by

mitosis.mitosis.Asexual Asexual

ReproductioReproductionn

Hydra(Budding)

The hydra is a tiny water animal that usually begins life as a bud that grows on the body of its parent. When fully developed, the young hydra detaches itself and lives independently.

Bacteria (Fission)Bacteria (Fission)

Streptococcus

Anthrax

Escherichia coli (E.coli)

PlanariaPlanaria(Regeneration)(Regeneration)

•Planarians normally reproduce by pulling in two.

•The fragments then regenerate their missing parts.

Sea StarsSea Stars

StrawberriesStrawberries(tubers)(tubers)

Houseplants (cuttings)

Advantages or Advantages or Disadvantage?Disadvantage?

• Only Only oneone parent is needed so the parent is needed so the organism can reproduce at organism can reproduce at anytime. anytime.

• Because there is only one Because there is only one “parent” there is no genetic “parent” there is no genetic variation. The “child” is an variation. The “child” is an exact exact duplicateduplicate..

Sexual ReproductionSexual Reproduction

• This occurs when This occurs when twotwo parent parent cells come together to form a cells come together to form a new organism (new organism (zygotezygote).).

• The parent cells often called The parent cells often called sex sex cellscells (eggs and sperm) are (eggs and sperm) are formed in a process called formed in a process called meiosismeiosis..

MeiosisMeiosis• When meiosis occurs the genetic When meiosis occurs the genetic

information is information is copied oncecopied once and the and the cell cell divides twicedivides twice. .

• Each new gamete cell contains only Each new gamete cell contains only one-halfone-half of the number of of the number of chromosomes of the parent cell.chromosomes of the parent cell.

• In humans the result is In humans the result is 4 sex cells4 sex cells each with each with 2323 chromosomes rather chromosomes rather than the usual than the usual 4646..

Sexual ReproductionSexual Reproduction• When the When the eggegg and the and the spermsperm unite unite

they form a new organism called a they form a new organism called a zygotezygote..

• In humans the offspring inherits In humans the offspring inherits 2323 chromosomes from the mother and chromosomes from the mother and 23 23 chromosomes from the father chromosomes from the father thus giving them a full set of thus giving them a full set of 46 46 chromosomeschromosomes..

• The offspring therefore has The offspring therefore has characteristicscharacteristics of both parents. of both parents.

Advantage or Advantage or Disadvantage?Disadvantage?

• Sexual reproduction results Sexual reproduction results in greater in greater genetic variation. genetic variation.

• Genetic variation is very Genetic variation is very beneficial in the process of beneficial in the process of natural selectionnatural selection..

• Sexual reproduction does Sexual reproduction does require require twotwo parents. parents.

Organisms that reproduce Organisms that reproduce SexuallySexually

LionsLions

DogsDogs

RabbitsRabbits

MosquitoesMosquitoes

SunflowersSunflowers

SalmonSalmon

PeoplePeople

How many How many organisms are organisms are

needed for asexual needed for asexual reproduction?reproduction?11

What is the end What is the end result of mitosis?result of mitosis?

2 identical daughter cells2 identical daughter cells

What are the What are the different uses for different uses for

mitosis?mitosis?New cells, growth and New cells, growth and development, reproductiondevelopment, reproduction

What are some What are some examples of examples of

organisms that organisms that reproduce reproduce asexually?asexually?

How many times is How many times is the genetic the genetic

information copied information copied in Meiosis?in Meiosis?11

How many times How many times does the cell divide does the cell divide

in meiosis?in meiosis?22

What is the end What is the end result of Meiosis?result of Meiosis?

4 cells with half as many 4 cells with half as many chromosomes.chromosomes.

Once the sperm Once the sperm fertilizes the egg in fertilizes the egg in a human how many a human how many chromosomes are chromosomes are

present in the present in the zygote? zygote?

23+23=4623+23=46

After fertilization After fertilization what process what process

allows the zygote allows the zygote to grow into a to grow into a

baby?baby?MitosisMitosis