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)

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 #

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 cycle

Divided into:◦ 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 haploidDifferentiate 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