the continuity of life. necessary for species to survive species ◦ closely related organisms...
TRANSCRIPT
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The Continuity of Life
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Necessary for species to survive
Species◦ Closely related organisms that share certain
characteristics and can produce new individuals through reproduction
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New organisms go through stages and grow into adulthood
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Division of the NUCLEUS!
◦ Asexual (mitosis)◦ Sexual (meiosis)
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Growth, repair, replacement of cells
To form sex cells (sperm and eggs) for reproduction
1 parent 1 division (2 cells) Identical offspring Rapid and high #
2 parents 2 divisions (4 cells) Varied offspring Slower and low #
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A series of events that occur in the life of a cell◦ Growth◦ Preparation for division◦ Division
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DNA: genetic material found in the nucleus of cells
Chromosome: organized structures of DNA and proteins found in cells
Chromatid: coiled DNA (forms ½ of the “X” shape)
Centromere: holds sister chromatids together
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Chromatin: uncoiled DNA (looks like spagetti)
Haploid: one set of chromosomes (in humans 23)
Diploid: double set of chromosomes (in humans 46)
Gametes: sex cells (sperm and eggs)
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Splitting of 1 cell into 2 cells evenly
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1 parent cell splits into 2 cells (unevenly)
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Mold spore cells reproduce mold (on the underside of leaves or on food)
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Re-growth of a body part
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Runners: strawberries Tubers: potatoes from stems Bulbs: underground stem Cutting: part of a plant gives rise to a new
plant Grafting: part of one plant attached to
another
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NUCLEAR DIVISION!◦ Nuclei divide to form 2 identical nuclei with the
same # of chromosomes◦ Cytoplasm pinches and divides to form 2
daughter cells
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IN between divisions
Period of growth for a cell when it replicates its DNA and centrioles and prepares for division
Longest period during the cell cycle
Divided into:◦ G1 – Growth◦ S – Synthesis of DNA
(duplication)◦ G2 – Growth and preparation for
division
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Prophase Metaphase Anaphase Telphase
Cytokinesis – occurs after Telophase but is not technically part of mitosis because the nucleus has already divided
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Chromatin condenses and coils into chromosomes
Centrioles separate Spindle apparatus forms Nuclear membrane breaks down
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Chromosomes line up across the center (midline)
Each chromosome is connected to a spindle fiber at its centromere
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Sister chromatids separate Individual chromatids are moved to the
poles (corners) of the cell.
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Chromosomes gather at opposite ends of the cell
Chromosomes loose their shape 2 nuclear membranes form
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Cytoplasm pinches in half (cleavage) and divides
Each daughter cell has an identical set of chromosomes (diploid)
Not part of mitosis
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Offspring receive half of their DNA from 1 parent and half form the other
No 2 organisms are exactly the same! The same to people will continue to produce
offspring that have different combinations of DNA
DNA is transferred by sex cells (gametes)
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Nuclear division of cells to create 4 daughter cells with a haploid (half #) set of chromosomes.
Used to produce SPERM AND EGGS for sexual reproduction (Gametogenesis)
2 Divisions to divide the # of chromosomes in half
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Chromosomes line up in pairs (diploid)
1st division (similar to mitosis)
2nd division (reduces chromosomes to ½)
Each daughter cell is haploid
Differentiate into 4 sperm with different combinations of chromosomes
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Chromosomes line up in pairs (diploid)
1st division (similar to mitosis)
2nd division (reduces chromosomes to ½)
Each daughter cell is haploidDifferentiate into 3 polar bodies and 1 viable egg
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The sorting of genes and recombining them during meiosis and fertilization creates variety◦ Variety is important for the survival of
species Mutations or changes in the chromosomes
can only be passed on to offspring if it occurs in the sex cells
DNA can be further varied during crossover in prophase 1
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Joining of sperm and egg (haploid) Forms a zygote (diploid) Can be external or internal
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Growth of a new organism from fertilization into adulthood
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Fish and amphibians◦Lay eggs and release sperm in the water◦Large number of eggs are released to
ensure survival◦Risky!◦Low survival rate◦Development occurs in the water
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Land animals – sperm is deposited in the body of the female
◦ Birds and reptiles: Fertilization occurs (forms eggs) Eggs continue to develop externally with some
parental care 3-7 eggs to ensure survival
◦ Mammals: Fertilization occurs and development is internal Lots of parental care 1-3 zygotes – high survival rate
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Zygote divides by mitosis to grow and become a developed multi-cellular organism
Early cells are identical to eachother (stem cells)
Stem cells can become any type of cells (like a blank slate)
Brain Pop video: Stem Cells
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Cells continue to divide and genes are activated or “turned on” creating different types of cells
Differentiated cells become specialized cells and tissues for form specific body organs and systems
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All cells in an organism contain the exact same DNA
Genes are activated in certain cells to specialize
Environmental factors can determine which genes are activated and how they are expressed
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Cells divide through mitosis 3 layers form an embryo
◦ Ectoderm (outer) – skin, hair, nails, nerves◦ Mesoderm (middle) – bones, muscles, blood◦ Endoderm (inner) – abdominal organs
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In water◦ Little or no parental care
On land◦ Some parental care◦ Differentiated layers form a protective shell that
cushions and supports the embryo◦ Yolk is the food source for the embryo
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Mammals◦ Embryo develops within the mother’s uterus◦ Receives nutrients from the placenta◦ High survival rate = less offspring
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Develops within the uterus during pregnancy
Umbilical cord connects the mother to the fetus
Exchange of nutrients, gases and waste The mother’s blood and baby’s blood are
never in direct contact
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Organized profile of a person’s chromosomes
Cell division is suspended at metaphase Chromosomes are cut and arranged by size
from largest to smallest 44 autosomes 2 sex chromosomes (XX or XY) Arrangement helps doctors and scientists
identify chromosomal abnormalities that may result in a genetic disorder
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An extra 21st chromosome (trisomy 21)is received during mitosis (the 21st chromosome fails to separate during anaphase and the daughter cell ends up with 24 chromosomes instead of 23)
The child now has 47 chromosomes instead of 46 Affects 1 in every 800 babies born Symptoms include: short stature, weak muscles,
short/wide neck, characteristic facial symptoms, intellectual disability and heart defects
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Extra “x” chromosome Affects 1 in every 700 males Signs include: lower IQ, slower development
and reduced fertility
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Single “x” chromosome Affects 1 in 2000 girls Signs include: short stature, broad chest,
non-working ovaries, amenorrhea, heart disease and memory deficiencies