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Which body system is the most important in maintaining the homeostasis (and survival) of an individual organism?
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Which body system is the most important in maintaining the homeostasis (and survival) of an individual organism?
Which body system is the most important in maintaining the survival of an entire species?
Reproduction
ReproductionThe life process by which an organism produces new individuals of the same kind.
This is essential for the survival of the species
Types of Reproduction
Asexual Reproduction Involves ________ parent and results in one or more offspring that are genetically _________ to that parent.
Cells reproduce by Mitosis
one
identical
MitosisA process where a cell divides and
creates two daughter cells which are identical to the parent
Cell Division happens by series of phases▪ Interphase, prophase, metaphase,anaphase, and telophase (cytokinesis)
▪ I.P.M.A.T.(C).
Overview of mitosis
interphase prophase
metaphase anaphase telophase
cytokinesis
I.P.M.A.T.C.
Please Make Another Two Cells
DNA must be duplicated…
nucleus
cell
DNA in chromosomes
nucleus
cell
duplicated chromosomes
chromosomes in cell
4 single-stranded chromosomes
duplicatedchromosomes
4 double-stranded chromosomes
Mitosis: Dividing DNA & cells
Stage 1: cell copies DNA
nucleus
cell
DNA Copy DNA!
INTERPHASE
Mitosis: Dividing DNA & cells
Stage 2: DNA winds into chromosomes Nuclear membrane disappears Spindle Fibers/ Centrioles appear
nucleus
cell
duplicated chromosomes Wind up!
PROPHASE
double-strandedhuman chromosomesready for mitosis
Mitosis: Dividing DNA & cells
Stage 3: Chromosomes line up in middle attached to protein “cables” that will
help them move
duplicated chromosomeslined up in middle of cell
Line up!
METAPHASE
Mitosis: Dividing DNA & cells
Stage 4: Chromosomes separate start moving to opposite ends
chromosomes split & move to opposite ends
Separate!
ANAPHASE
Mitosis: Dividing DNA & cells
Stage 5: Cell starts to divide Two nuclei Chromosomes unwind
Divide!
TELOPHASE
Mitosis: Dividing DNA & cells
Stage 6: DNA unwinds again cells separate completely (cleavage
furrow) now they can do their every day jobsBye Bye!
CYTOKINESIS
Biology is the only subject in which
multiplication is the same thing as division…
Examples of Asexual Reproduction
Binary Fission The cell splits into two identical cells, each containing an exact copy of the original cell's DNA.
Nucleus and Cytoplasm divide EQUALLY!
Examples of Asexual Reproduction
Budding- where the daughter cell grows out of
the parent and gradually increases in size.
Yeast cells
Hydra
Nucleus divides equally Cytoplasm divides unequally
Examples of Asexual ReproductionSpores Reproductive cell that contains a
nucleus and a small amount of cytoplasm
Spores are highly resistant to heat Spores are capable of growing into a
new organism when conditions allow Produced by bread mold, mushrooms,
mosses and ferns
Examples of Asexual Reproduction
Regeneration Development of a new organism from
part of a parent Whole organisms are produced – Starfish! Replacement of lost body part
Examples of Asexual Reproduction
Vegetative Propagation Part of a plant (root, stem, leaves) grows
into a new plant Seedless fruits & vegetables Commonly used by farmers = quick, easy
& successful!
Sexual Reproduction
Offspring receive half of their genes from one parent and half from the other parent
The genes are carried on chromosomes in sex cells known as gametes
Male gamete is the sperm cell
Female gamete is the ovum (egg)
Sexual Reproduction Joining of 2 sex cells (egg & sperm) Do we make egg & sperm by
mitosis?
46 46+ 92
egg sperm zygote
What if we did, then….
Doesn’t work!
No!
Sexual ReproductionGametes are formed by Meiosis
Meiosis (reduction division) In series of divisions the number of chromosomes is reduced by half
Meiosis makes sperm & eggs
46 chromosomes to 23 chromosomes half the number of chromosomes
23
2346
egg
sperm
46
meiosis
haploiddiploid
Sexual Reproduction
FertilizationTwo gametes (Ovum and Sperm) join to create an offspring
Variation Each offspring gets a unique combination of genes, therefore they are not identical to their parents or siblings.
Sexual Reproduction
Meiosis (reduction division)
Spermatogenesis: Creates 4 sperm cells
Oogenesis: Creates 1 ovum and 3 polar bodies
mitosis
zygote
Putting it all together…
23
2346
egg
sperm
46
meiosis 4623
23
fertilization mitosis &development
meiosis fertilization mitosis + development
46
46
46
46
46
4646 46
gametes
Meiosis & mitosis
Meiosis to make gametes sperm & egg
Mitosis to make copies of cells growth repair Development replacement
The value of meiosis 1 Consistency over time
meiosis keeps chromosome number same from generation to generation
from Mom
from Dad
offspring
Dad
Mom
The value of meiosis 2 Change over time
meiosis introduces genetic variation▪ gametes of offspring do not have
same genes as gametes from parents▪ new combinations of traits
from Mom
from Dad
new gametes made by offspring
offspring
We’remixing thingsup here!
variation
Adding to Variation…
Crossing Over – Trading DNA!
During prophase 1, sister chromatids intertwine homologous pairs swap
pieces of chromosome▪ DNA breaks & re-
attaches
tetrad
prophase 1
Sexual reproduction creates variabilitySexual reproduction allows us to maintain both genetic similarity & differences.
Baldwin brothers
JonasBrothers
Martin & Charlie Sheen, Emilio Estevez
CloningA form of asexual reproduction
The nucleus is taken from parent with a complete set of genetic information
Injected into an egg cell which has had its nucleus removed
Cloning cont.The egg is implanted in a surrogate mother
Result is an organism which is 100% genetically identical to parent
