How do organisms grow?
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Transcript of How do organisms grow?
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How do organisms grow?
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How do organisms grow?
Paramecium 400xOnion skin cells 400x
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How do organisms grow?
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How do organisms grow?• Living things grow by producing
more cells.• Cells will divide rather than
growing larger.• The larger a cell becomes, the
more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and waste across cell membrane.
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The cell
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BASIC GENETICS• Each cell in the human body contains two sets
of 23 chromosomes
• Mitosis identically replicates this information
• Each cell therefore has the same genetic material
• Reproductive cells only have one set of chromosomes. These combine to make a new person with different genetic material to both parents
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Replication
Chromosomes, Chromatids and Centromeres
Centromere
Chromosome arm
Chromosome arm
Identicalchromatid
Chromatid
Anaphase
A packaged chromosome
Two identical chromosomes
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Chromosomes
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Sister Chromatids
Spindle fiberscentromerre
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The Cell Cycle
• The series of events that cells go through as they grow and divide
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Cell Cyclehttp://www.cellsalive.com/cell_cycle.htm
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Cell Cycle
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Interphase
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The Cell CycleInterphase:
• G1: The cell grows and does its job (produce proteins).
• S: The cell will replicate (copy) the chromosomes.
• G2 : The cell makes copies of all the other organelles.
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Mitosis: PMAT
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Mitosis• All daughter cells
contain the same genetic information from the original parent cell from which it was copied.
• Every different type cell in your body contains the same genes, but only some act to make the cells specialise – e.g. into nerve or muscle tissue.
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The Spindle A spindle is a web type structure made
up of microtubule fibers. It is essential for mitosis because it arranges the chromosomes into their correct positions in preparation for cell division. Mitotic center
MicrotubuleA cell at metaphase a spindle
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mitosis
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Mitosis (M Phase): How the Cells Divide:
• Used for asexual reproduction as well as for growth and repair
• There are four stages:• PMAT ( Prophase, Metaphase,
Anaphase and Telophase)
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Prophase• Chromatin
condenses into chromosomes.
• The centrioles migrate to opposite ends of the cell.
• Spindle fibers and the aster forms.
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Late Prophase• The spindle
fibers have attached themselves to the chromosomes.
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Metaphase• The chromosomes migrate to the equator (middle) of the cell.
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Anaphase• Begins with
the separation of the sister chromatids,
• by pulling chromosomes to opposite ends of the cell.
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Telophase• the chromosomes
reach the ends of their respective sides, the nuclear envelope reforms.
• There are now two smaller cells each with exactly the same genetic information.
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Cytokinesis
• Division of cytoplasm
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Summarize each phase in your own words
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Asexual Reproduction• the cell just
divides into two identical cells.
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Advantages:
• Widely dispersed populations can still reproduce.
• Cells are identical to parents and should survive well if conditions don't change.
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Disadvantages:
• Cells are identical to parents and so are vulnerable to the same environmental stresses.
• The characteristics of the cells change very slowly
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Regeneration
• Echinoderms exhibit this type of reproduction
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Regeneration
• A piece of a parent is detached, it can grow and develop into a completely new individual
Planarians exhibit this type of reproduction.
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binary fission • involves an
equal division of both the organism cytoplasm and nucleus to form two identical organisms. Paramecium
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Budding • one parent
dividing its nucleus (genetic material) equally, but cytoplasm unequally
• Hydras, yeasts exhibit this type of reproduction.
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Parthenogenesis• ("virgin birth"), the
females produce eggs, but these develop into young without ever being fertilized.
• occurs in some fishes, several kinds of insects, and a few species of lizards.
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sporulation (spore formation)
• reproduction involving specialized single cells coming from one parent
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Vegetative Propagation
• the ability of plants to reproduce without sexual reproduction, by producing new plants from existing vegetative structures.
• Vegetative propagation is an example of asexual reproduction.
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Natural vegetative propagation
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Vegetative Propagation
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Vegetative Propagationrunner
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Artificial Vegetative Propagation Cutting
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Artificial Vegetative propagationgrafting
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Telomeres
• Telomeres are specialized chromosome tips.
• Telomeres are lost during cell division. This causes the chromosomes to SHORTEN each time they divide.
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How is the cell cycle regulated?
• Biochemical checkpoints--a clock provided by shortening chromosome tips, and chemical signals from outside and inside the cell--regulate the cell cycle.
• Stem cells maintain the growth and specialization of a tissue.
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Stem cells
• Stem cells are capable of producing specialized cells throughout the body. When a stem cell divides to form two new daughter cells, one specializes (to form a skin cell for example) while the other remains a stem cell--ready to divide again. As a result, skin cells can be replaced without having to divide themselves.
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Cell division
All complex organisms originated from a single fertilized egg.
Every cell in your body started here, through cell division the numbers are increased
Cell then specialize and change into their various roles
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Cancer--When the Cell Cycle Goes Awry
• cancer cells repeatedly go through the cell cycle and, essentially, never die…they continue to grow uncontrollably.
• Cancer is caused by a series of genetic mutations leading to the development of a tumor (an abnormal mass of cells).
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Big IDEA: Sexual Reproduction
• This process involves two parents.
• Both parents contribute one gamete or sex cell to the process.
• The genetic information given to the offspring will be obtained equally from each parent.
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Meiosis
• The process that produces gametes or sex cells.
• Occurs in the reproductive organs . • Before meiosis occurs the cell
duplicates its chromosomes. It halves the chromosome number from the original parent cell in the four cells it forms.
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Prophase I :• Synapsis: The
chromatid pairs pair up with their homologous pair, forming a tetrad.
• This tetrad contains 2 original homologous chromosomes and their duplicates.
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Prophase I (con’t)• The process of
crossing over occurs during this time allowing for genetic diversity in the genome.
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Metaphase I : • Tetrads line up
along the center (equator) of the cell.
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Anaphase I : • The tetrads split
and move in opposite directions. During this phase the chromatid pairs move away from each other.
• (1 cell )
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Telophase I :• Telophase I : Two
cells form each containing a complete set of chromosomes in the form of chromatid pairs. (2 cells )
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Prophase II• The process
continues moving the chromatid pairs toward the center of the cell.
• (2 cells )
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Metaphase II :• The chromatid
pairs line up along the center of the cell.
• (2 cells )
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Anaphase II :• The chromatid
pairs split moving the individual chromosomes toward the opposite poles.
• (2 cells )
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Telophase II :• Each of the two cells will begin to split in half and produce 2 more cells bringing the total to 4 cells. Each of these cells contain 1/2 the normal number of chromosomes.
• ( 4 cells )
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Gametogenesis
• Meiosis occurs in the gonads (sex organs).
• Testes of the male and is called spermatogenesis.
• The ovaries of the female and called oogenesis.
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Oogenesis
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Oogenesis• The production of eggs (ovum).• Eggs develop in the ovary from cells called
primary oocytes (parent cells).• Meiosis in the primary oocyte results in the
formation of one ovum and three cells called polar bodies.
• The egg contains stored nutrients (yolk) and can not move.
• Polar bodies have the same number of chromosomes as egg but less cytoplasm
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Egg cell
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Spermatogenesis• Four sperm cells are
produced from each primary spermatocyte (parent cell) in the tesitis
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Sperm cell• Head made of
nucleus that contains chromosomes and acrosome.
• Mid piece made up of mitochondria.,
• Flagellum is a whiplike tail.
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Compare the ovum/sperm
• Size• Motility• Number of
chromosomes• Food
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Fertilization
• Union of egg and sperm produce a zygote.
• n (sperm) + n (egg) ->2n(zygote)• (n=the number of chromosomes)• 23 chromosomes in one sperm + 23
chromosomes in one egg 46 chromosomes in zygote (fertilizated egg)
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Fertilization
• After penetration of sperm head, fertilization envelope forms
• Prevents other sperms from entering