Key Idea # 9

All organisms have a life span and must reproduce in order to continue the species.

Reproduction

allows the genetic material of living things to be passed from generation to generation

is required for the survival of a species includes two types:

– sexual– asexual

Asexual Reproduction

Advantages: only one parent is needed offspring are genetically identical to parent can produce large numbers of offspring

Disadvantages: no genetic variety because offspring are

genetically identical to the parent organisms are all identical so the species can’t

adapt to a changing environment

Types of asexual reproduction include:

runners bulbs tubers budding binary fission fragmentation regeneration cloning

FYI: Fragmentation and Regeneration

A type of asexual reproduction found in less evolved animals.

When the parent body breaks into pieces, each piece can grow into a new organism that is identical to the parent.

http://images.google.com/imgres?imgurl=http://image.tutorvista.com/content/reproduction/planaria-regeneration.jpeg&imgrefurl=http://www.tutorvista.com/content/science/science-ii/reproduction/asexual-reproduction.php&usg=__RTk4xJj77XukAzKY23f81XPmc1o=&h=371&w=415&sz=16&hl=en&start=28&um=1&itbs=1&tbnid=AO9LlKVsW0u0XM:&tbnh=112&tbnw=125&prev=/images%3Fq%3Dregeneration%2Band%2Bfragmentation%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D20%26um%3D1

http://web.mit.edu/neuro/planaria.html

Sexual ReproductionAdvantages: Genetic variety

• organisms closely resemble their parents• both parents contribute an equal amount of genetic

material to the offspring.

Organisms have a greater chance of adapting to environmental changes

Disadvantages: Two organisms must be involved Some genetic combinations can negatively affect the

survival of some species by passing on diseases and genetic defects

Some organisms reproduce in more than one way……

Yeast Reproduction

Bacteria reproduce

Asexually genetic material is duplicated before the cell divides

resulting in two daughter cells that are genetically identical to each other.– Note: a disadvantage is antibiotics will kill all bacteria

Sexually genetic material is transferred from one cell to

another cell forming one new bacteria cell that is genetically different from the parent cells – Note: An advantage is antibiotic resistance in offspring.

http://biology.about.com/od/bacteriology/a/aa080907a.htm

Plants reproduce

sexually through pollination and fertilization

asexually through production of runners, tubers, regeneration, bulbs cloning, etc…

What about fraternal and identical twins?

Fraternal Twins are produced when two separate sperm cells

fertilize two different egg cells by sexual reproduction.

are not identical because they have different DNA (chromosomes and genes)

http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm

Identical Twins

are produced after one sperm cell fertilizes an egg cell by sexual reproduction and the fertilized egg divides into two fertilized egg cells by asexual reproduction.

are identical because they have identical DNA (chromosomes and genes).

http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm

Cell Division

is the process by which a cell divides to form two identical daughter cells.

Googleimages.com

Cell Growth and Cell Division

The daughter cells grow and increase in size until they reach maturity.

Once the daughter cells reach maturity, they divide and produce two more daughter cells.

This process continues, resulting in organism growth and reproduction of cells.

Googleimages.com

The Cell Cycle Each time cell division takes place, it’s called

a cell cycle For unicellular organisms, a cell cycle results

in a new organism– bacteria, amoeba, paramecium

For multicellular organisms, a cell cycle results in a new cell – leaf cells, root cells, skin cells, blood cells, etc.

The growth of a unicellular organism is limited to an increase in cell size.

Once unicellular organisms reach adulthood they divide.

The 12 small cells near the top of this colony only swim.

The 20 larger adult cells both swim and reproduce by cell division.

Pleodorina starrii

http://www.sciencedaily.com/images/2009/02/090219140546-large.jpg (Credit: Copyright 2008 Matthew Herron)

Bacteria

are unicellular organisms without a nucleus

will reproduce every 20 minutes under ideal conditions

How do cells reproduce? 

Prokaryote cells like bacteria don’t have organelles and a nucleus to divide up, so they can divide by splitting themselves in two by binary fission.

Eukaryote cells like animal and plant cells

have organelles and a nucleus to divide so they must undergo mitosis.

http://74.125.95.132/search?q=cache:-HB2ovA-4l8J:teachers.henrico.k12.va.us/deeprun/chapman_j/unit05/cell_division.ppt+skin+cell+reproduction&cd=6&hl=en&ct=clnk&gl=us

Binary Fission

The cell duplicates its genetic material and then divides into two separate cells

Mitosis produces two new

daughter cells which are identical to each other and the original parent cell.

produces body cells for growth, replacement, and repair

Note: A similar type of cell division occurs in plant cells

Googleimages.com

FYI: Cell Replacement Bone marrow cells constantly divide to

produce new red and white blood cells – RBC’s live about 100-120 days– WBC’s live about 13-20 days

Skin cells under your epidermis constantly divide and move upward to replace lost skin cells that flake off. – Most people re-grow their epidermis

completely about every two years.

Kidshealth.org

Are a child’s cells smaller or the same size as it’s parents'?

You might think that the parents have larger cells, because their bodies are bigger. But the truth is, that both the infant, its parents, have cells that are pretty much the same size. However, the parents have a lot more cells.

http://www.kidsbiology.com/biology_basics/index.php

Growth of multi-cellular organisms is due to both an increase in cell size and an increase in cell number.

http://schulen.eduhi.at/hsgunskirchen/hot_pot/English/More1/family_clipart.jpg

Once cells in multi-celled organisms reach adulthood they divide (reproduce) and form two cells.

Repeated cell division causes an increase in cell number in the organism.

A larger multi-cellular organism has more cells than a smaller organism of the same species, but the cells are all pretty much the same size.

http://www.microscopy-uk.org.uk/mag/imgaug99/whole.jpg

http://anubis.ru.ac.za/Main/ANATOMY/celldiv.jpg

FYI Meiosis: is a type of cell division that

produces sex cells for reproduction

produces 4 new daughter cells which only have half of the genes from the original parent cell.

When these cells combine to produce offspring each contributes half the genes that a normal body cell contains

Produces Body Cells Produces Reproductive Cells

http://www.bio.georgiasouthern.edu/biohome/harvey/lect/images/comparison.gif

Life Cycle of the Flowering Plant: Produces Plant Cells