Download REPRODUCTION & DEVELOPMENT

The Continuity of Life

Necessary for species to survive

Species
◦ Closely related organisms that share certain
characteristics and can produce new individuals
through reproduction

New organisms
go through
stages and grow
into adulthood

Division of the NUCLEUS!
◦ Asexual (mitosis)
◦ Sexual (meiosis)




1 parent
1 division (2 cells)
Identical offspring
Rapid and high #
Growth, repair,
replacement of cells




2 parents
2 divisions (4 cells)
Varied offspring
Slower and low #
To form sex cells (sperm
and eggs) for
reproduction

A series of events that occur in the life of a
cell
◦ Growth
◦ Preparation for division
◦ Division




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




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)

Splitting of 1 cell into 2 cells evenly

1 parent cell splits into 2 cells (unevenly)

Mold spore cells reproduce mold (on the
underside of leaves or on food)

Re-growth of a body part





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

NUCLEAR DIVISION!
◦ Nuclei divide to form 2 identical nuclei with the
same # of chromosomes
◦ Cytoplasm pinches and divides to form 2 daughter
cells


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

Divided into:
cycle
◦ G1 – Growth
◦ S – Synthesis of DNA (duplication)
◦ G2 – Growth and preparation for
division





Prophase
Metaphase
Anaphase
Telphase
Cytokinesis – occurs after Telophase but is
not technically part of mitosis because the
nucleus has already divided




Chromatin condenses and coils into
chromosomes
Centrioles separate
Spindle apparatus forms
Nuclear membrane breaks down


Chromosomes line up across the center
(midline)
Each chromosome is connected to a spindle
fiber at its centromere


Sister chromatids separate
Individual chromatids are moved to the poles
(corners) of the cell.



Chromosomes gather at opposite ends of the
cell
Chromosomes loose their shape
2 nuclear membranes form



Cytoplasm pinches in half (cleavage) and
divides
Each daughter cell has an identical set of
chromosomes (diploid)
Not part of mitosis




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)



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




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




Chromosomes line up in
pairs (diploid)
1st division (similar to
mitosis)
2nd division (reduces
chromosomes to ½)
Each daughter cell is
haploid
Differentiate into 3 polar bodies and 1 viable egg

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



Joining of sperm and egg (haploid)
Forms a zygote (diploid)
Can be external or internal

Growth of a new organism from fertilization
into adulthood

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

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




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


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



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


Cells divide through mitosis
3 layers form an embryo
◦ Ectoderm (outer) – skin, hair, nails, nerves
◦ Mesoderm (middle) – bones, muscles, blood
◦ Endoderm (inner) – abdominal organs


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

Mammals
◦ Embryo develops within the mother’s uterus
◦ Receives nutrients from the placenta
◦ High survival rate = less offspring




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






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




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



Extra “x” chromosome
Affects 1 in every 700 males
Signs include: lower IQ, slower development
and reduced fertility



Single “x” chromosome
Affects 1 in 2000 girls
Signs include: short stature, broad chest,
non-working ovaries, amenorrhea, heart
disease and memory deficiencies