Section 5.4: Asexual Reproduction Biology

Types of Reproduction Sexual Reproduction Joining of gametes (sperm and eggs), one from each parent Genetically unique offspring Asexual Reproduction Creation of offspring from a single parent Genetically identical to each other and the parent organism

Binary Fission Way that prokaryotes reproduce Asexual reproduction of single-celled organisms Very similar to mitosis, with similar results Formation of two daughter cells that are identical to the parent cell

Steps of Binary Fission DNA is duplicated and chromosomes are attached to the cell membrane Bacteria cell grows and elongates When cell is approximately twice its normal size it undergoes cytokinesis New cell is laid down between the two sets of DNA and two daughter cells are formed

Advantages to Asexual Reproduction More efficient Decreased genetic variation if cells are suited to the environment they are currently residing in

Disadvantages to Asexual Reproduction No genetic variation can be bad if cell is living in an environment that changes routinely An entire generation or population can die off Decreased genetic variation also decreases the likelihood that one or more offspring will survive should conditions change

Asexual Versus Sexual Reproduction Sexual reproduction requires a lot of energy Attract a mate and all of the behaviors and signals required for that Sexual reproduction also decreases the number of members within the population that can produce offspring Asexual reproduction can produce more offspring, quicker, with less cost But is it really less cost if the diversity is decreased?

Eukaryotes Reproducing Through Mitosis Eukaryotes can reproduce asexually through mitosis Common in simple plants and animals Three Types: Budding Fragmentation Vegetative Reproduction

Budding Small projection grows from parent organism This will be come a new individual May live independently or as an attached colony Example: Yeast

Fragmentation Parent organism splits into pieces which can all grow into new organisms Examples: Sea Stars Flatworms

Vegetative Reproduction Modification of stem and underground structures of parent organism Offspring stay connected to parent organism through structures called runners Examples: Strawberries Potatoes

Doing It All Some organisms can reproduce both asexually and sexually Generally depends upon the current conditions Sea Anemone Binary Fission Budding Fragmentation Sexually with eggs and sperm

Section 5.5: Multicellular Life Biology

Multicellular Organisms Cells need to work together to form larger, more complex structures Tissues: groups of cells that work together to perform a similar function Organs: groups of tissues that work together to perform a specific function or related functions Organ Systems: Organs that carry out similar functions All organ systems work together to help the organism maintain homeostasis

Cell Differentiation Multicellular life requires that there are many cells performing specific functions But you start as a fertilized egg, essentially one cell How do you get to be whole person? Cell differentiation: The process by which unspecialized cells develop into their mature forms and function

Cell Differentiation All cells contain all of your DNA But only some of that DNA is used Certain cell types use specific genes within the DNA, and turn off the rest A cell’s location within an embryo determines how it will differentiate Inner, middle, and outer layers of an embryo become different tissues and organs

Stem Cells Unique type of body cell that have the ability to: Divide and renew themselves for long periods of time Remain undifferentiated in form Develop into a variety of specialized cell types Can divide into: 2 new stem cells 1 new stem cell and 1 specialized cell

Stem Cell Classification Types of stem cell are categorized according to their potential to develop into different cell types Totipotent: Can grow into any cell type Only fertilized eggs and first few divisions Pluripotent: Can grow into any cell type except for totipotent Multipotent: Grow into cell type that are of a closely related family

Stem Cell Classification May also be classified by their origin Adult Stem Cells Embryonic Stem Cells

Adult Stem Cells Undifferentiated cells located among the specialized cells of many organs and tissues Also found in umbilical cord blood Can be taken from patient, grown in culture, and put back into the patient No rejection by patient’s immune system Few in number, hard to isolate, and tricky to grow Can contain DNA abnormalities Previously thought that only multipotent Research has shown that the addition of specific molecules at the right time might be able to make these cell pluripotent

Embryonic Stem Cells Taken from donated embryos left over from in vitro fertilization Three to five day old embryo True pluripotent cells that can turn into any of the 200 different cell types of the body Can be rejected by patient’s immune system, or grow a tumor Ethical questions surrounding the destruction of the embryo to harvest

Use of Stem Cells Used to treat patients with leukemia and lymphoma Current research in use of stem cells for diabetes Growth of new organs from stem cells, or repair of damaged sections of an organ with specialized stem cells Stem cells are also useful when testing new compounds, as the cells can be grown into any tissue, without having that tissue come from or be attached to a currently living human

Review Questions Page 150 # 2, 3, and 5 Page 155 #1-5 Answer all questions in complete sentences.