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Life Science Review
Chloroplast- The cell organelle in which photosynthesis takes place. In this organelle the light
energy of the sun is converted into chemical energy.
Chloroplasts are found only in plant cells not animal cells. The chemical energy that is produced
by chloroplasts is finally used to make carbohydrates like starch, that get stored in the plant.
Chloroplasts contain tiny pigments called chlorophylls. Chlorophylls are responsible for trapping
the light energy from the sun.
Differences between Prokaryotic & Eukaryotic cells
Bacterial cells also contain flagellum, plasmid and capsule.
Feature
Size
Genetic
material
Organelles
Cell walls
Ribosome’s
Prokaryote
Eukaryote
Small about 0.5
micrometers
Up to 40 micrometers
Circular DNA (in
cytoplasm)
DNA in form of linear
chromosomes ( in nucleus)
Few present, none
membrane bound
Rigid formed from
glycoproteins (mainly
murein)
70s
Many organelles:
•Double membranes e.g.:
nucleus, mitochondria &
chloroplasts
•Single membrane e.g.: GA,
ER & lysosomes
•Fungi: rigid, formed from
polysaccharide, chitin.
•Plant: rigid, formed from
polysaccharides. E.g.:
cellulose.
•Animals no cell wall
80s
Definitions and plant cell parts.
Cytoplasm-gel like substance found in a cell
Chloroplasts-a green structure in a plant
Cell Wall-a stiff covering that protects plant
cells
Nucleus-control center of the cell
Chromosomes-provides direction for cell to
follow
Endoplasmic Reticulum-transportation
network
Mitchondrion-produces energy in the cell
Vacuole-cell storage sac for food, waste and
water
Parts of the animal cell and definition.
Vacuole-cell storage sac for food,waste, and
water
Mitochondrion –produces energy in a cell
Chromosomes-provides direction for cells to follow
Nucleus-control center of a cell
Endoplasmic Reticulum--transporation system
Cytoplasm-gel like substance found in a cell
Cell Membrane-surrounds cell material
Cells also carry out diffusion,passive
transport active transport and
osmosis.
Diffusion-movement of gases from higher
concentrations to lower concentrations
Passive Transport-materials do not need
energy to move from higher concentration
to lower to a lower concentration
Active Transport-materials need energy to
move from a higher concentration to lower
concentration
Osmosis-water moving from higher
concentration to a lower concentration
DNA is a double helix
• All DNA Is made up of 3 parts
– Phosphate group
– 5 sugar deoxyribose
– Nitrogen Base
What are the four bases?
• Pyrimidine: Only one
ring
– Thymine (T)
– Cytosine (C)
• Purines; 2 rings
– Adenine (A)
– Guanine (G)
The backbone is connected by covalent bonds.
The bases are connected by hydrogen bonds.
hydrogen bond
covalent bond
Replication copies the genetic information.
• A single strand of DNA serves as a
template for a new strand.
• The rules of base pairing direct
replication.
• DNA is replicated during the
S (synthesis) stage of the
cell cycle.
• Each body cell gets a
complete set of
identical DNA.
A Model used to show the
possible ways genes can
combine during fertilization.
Dominant and recessive alleles
are represented by letters.
Punnett Squares
A capital letter (T) is used for
dominant alleles.
A lowercase letter (t) is
used for recessive alleles.
Punnett Squares
The letters representing the alleles from one
parent are placed along the top of the
square.
T
t
Punnett Squares
T t xT t
T
T
t
t
Punnett Squares
Squares are filled by writing the letter at the top beside the
letter on the side.
T
T
t
t
TT
Tt
Tt
tt
Punnett Squares
The letters in each of the squares represents
the Genotypes of the offspring that the
parents could produce.
T
T
t
t
TT
Tt
Tt
tt
TT
Tt
Tt
tt
Punnett Squares
The genotype (genetic makeup) can
be used to predict the phenotype
(physical appearance) of the
offspring.
Punnett Sqaures
Genotype
TT
Tt
Tt
tt
Phenotype
tall
tall
tall
short
1.
2.
3.
4.
Chromosomes, Genes, and Genetic Crosses
Homologous
Chromosomes contain
genes (locations) for the
same traits
Traits are controlled by
alleles (alternative forms
of a gene).
Genotype refers to the
alleles an individual
receives at fertilization
Phenotype refers to the
physical appearance
of the individual.
5. Homozygous dominant genotypes =
two dominant alleles for a trait. (BB)
6. Homozygous recessive genotypes =
possess two recessive alleles for a trait (bb)
7. Heterozygous genotypes =
one of each allele for a particular trait (Bb)
Punnett Squares
Probability: the ratio that a particular event could occur.
3 would be tall
out of 4 offspring
1 would be short
Punnett Squares:
•Help you keep track of traits.
•Predict genotype and phenotype.
•Calculate probability.
Cell Cycle
• During the cell cycle, a cell grows, prepares for
division, and divides to form 2 daughter cells,
each with each of which then begins the cycle
again.
• Interphase – time for growth and regular cell
activity.
• Most of a cells life is spent in Interphase.
Mitosis
• The division of somatic or regular cells.
• Its divided into 4 phases.
• Remember Interphase is NOT part of Mitosis.
Prophase
• First stage of Mitosis
• Chromatin condenses into chromosomes
• Centrioles separate and a spindle fiber begins
to form.
• Nuclear membrane breaks down
Metaphase
• Second Phase of Mitosis
• Chromosomes line up in the middle of the
cell.
• Each chromosome is connected to a spindle
fiber.
Anaphase
• Third Phase of Mitosis
• The sister chromatids separate into individual
chromosomes and move apart to opposite
ends of the cell.
Telophase
• Fourth and Final Stage of Mitosis
• Chromosomes gather at opposite ends of the
cell and lose their distinct shapes
• Two new nuclear membranes have formed.
Cytokinesis
• The cytoplasm pinches in half.
• Each daughter cell has an identical set of
duplicate chromosomes
Regulating the Cycle
• A protein call cyclin helps regulate the cell
cycle in eukaryotic cells.
• They respond to internal and external events.
These proteins are regulators.
When Things Go Wrong
• Cancer cells do not respond to the signals that
regulate the growth of most cells.
• As a result, they form masses of cells called
tumors that can damage surrounding tissues.
• Asexual
Reproduction
– Many single-celled organisms reproduce by
splitting, budding, parthenogenesis.
– Some multicellular organisms can reproduce
asexually, produce clones (offspring genetically
identical to parent).
Meiosis KM
37
Chromosomes
• Karyotype:
– ordered display of an individual’s chromosomes.
– Collection of chromosomes from mitotic cells.
– Staining can reveal visible band patterns, gross
anomalies.
Meiosis KM
38
In humans …
• 23 chromosomes donated by each parent (total =
46 or 23 pairs).
• Gametes (sperm/ova):
– Contain 22 autosomes and 1 sex chromosome.
– Are haploid (haploid number “n” = 23 in humans).
• Fertilization/syngamy results in zygote with 2
haploid sets of chromosomes - now diploid.
– Diploid cell; 2n = 46. (n=23 in humans)
• Most cells in the body produced by mitosis.
• Only gametes are produced by meiosis.
Meiosis KM
39
Chromosome numbers
All are even numbers –
diploid (2n) sets of
homologous
chromosomes!
Meiosis KM
40
Ploidy = number of
copies of each
chromosome.
Diploidy
Meiosis – key differences from
mitosis
Meiosis reduces the number of chromosomes by half.
•
• Daughter cells differ from parent, and each other.
• Meiosis involves two divisions, Mitosis only one.
• Meiosis I involves:
– Synapsis – homologous chromosomes pair up. Chiasmata
form (crossing over of non-sister chromatids).
– In Metaphase I, homologous pairs line up at metaphase
plate.
– In Anaphase I, sister chromatids do NOT separate.
– Overall, separation of homologous pairs of chromosomes,
rather than sister chromatids of individual chromosome.
Meiosis KM
41
Meiosis KM
42
Animation
Meiosis KM
43
Meiosis 1
First division of meiosis
• Prophase 1: Each chromosome dupicates and
remains closely associated. These are called sister
chromatids. Crossing-over can occur during the
latter part of this stage.
• Metaphase 1: Homologous chromosomes align at
the equatorial plate.
• Anaphase 1: Homologous pairs separate with
sister chromatids remaining together.
• Telophase 1: Two daughter cells are formed with
each daughter containing only one chromosome
of the homologous pair.
Meiosis KM
44
Meiosis II
Second division of meiosis: Gamete formation
• Prophase 2: DNA does not replicate.
• Metaphase 2: Chromosomes align at the
equatorial plate.
• Anaphase 2: Centromeres divide and sister
chromatids migrate separately to each
pole.
• Telophase 2: Cell division is complete. Four
haploid daughter cells are obtained.
Meiosis KM
45
Mitosis vs. meiosis
Meiosis KM
46
Meiosis KM
47
Meiosis creates genetic variation
• During normal cell growth, mitosis produces
daughter cells identical to parent cell (2n to 2n)
• Meiosis results in genetic variation by shuffling of
maternal and paternal chromosomes and crossing
over.
No daughter cells formed during meiosis are
genetically identical to either mother or father
During sexual reproduction, fusion of the
unique haploid gametes produces truly unique
offspring.
Meiosis KM
48
In humans
e.g. 23 chromosomes in haploid
2n = 46; n = 23
2n = 223 = ~ 8 million possible combinations!
Meiosis KM
49
Crossing over
Chiasmata – sites of crossing over, occur
in synapsis. Exchange of genetic
material between non-sister chromatids.
Crossing over produces recombinant
chromosomes.
Meiosis KM
50
Sex is costly!
• Large amounts of energy required to find a mate
and do the mating: specialized structures and
behavior required
• Intimate contact provides route for infection by
parasites (AIDS, syphillis, etc.)
• Genetic costs: in sex, we pass on only half of
genes to offspring.
• Males are an expensive luxury - in most species
they contribute little to rearing offspring.
Meiosis KM
51
But …
• More genetic diversity: more potential for survival of
species when environmental conditions change.
– Shuffling of genes in meiosis
– Crossing-over in meiosis
– Fertilization: combines genes from 2 separate individuals
• DNA back-up and repair.
– Asexual organisms don't have back-up copies of genes,
sexual organisms have 2 sets of chromosomes and one can
act as a back-up if the other is damaged.
– Sexual mechanisms, especially recombination, are used to
repair damaged DNA - the undamaged chromosome acts as
a template and eventually both chromosomes end up with
the correct gene.
Meiosis KM
52
Levels of Organization
Remember, the human body is organized in several levels, from the simplest to the most
complex. . .
Cells – the basic unit of life
Tissues – clusters of cells performing a similar function
Organs – made of tissues that perform one specific
function
Organ Systems – groups of organs that perform a
specific purpose in the human body
***The purpose of the 11 organ systems is for the human body to maintain homeostasis.
The 11 Human Body Systems
The 11 human body systems are as follows:
-- nervous system
-- integumentary system
-- respiratory system
-- digestive system
-- excretory system
-- skeletal system
-- muscular system
-- circulatory system
-- endocrine system
-- reproductive system
-- lymphatic (immune) system
The Digestive System
Purpose: to convert food particles into simpler
micromolecules that can be absorbed into the
body
bloodstream and used by the
Major Organs and their Functions:
Mouth – to chew and grind up food
-- saliva also begins the chemical breakdown
Esophagus – pipe connecting mouth to stomach
Stomach – secretes an extraordinarily strong acid (pH = 2) that
breakdown of food
leads to
-- once the food is broken down in the stomach and
digestive juices, it is called chyme
mixed with
Pancreas – produces the hormone insulin that regulates blood
sugar levels
-- also help neutralize stomach acid
Liver – produces bile, which breaks down fats in foods
Gallbladder – pouch-like organ that stores bile for future use
Small Intestine – after digestion is complete, the chyme enters the small intestine where it
is absorbed into the bloodstream
-- the chyme is propelled along by folded surfaces
called villi, on the
intestine
Large Intestine – removes water from the chyme and gets the waste ready for excretion
The Excretory System
Purpose: to rid the body of wastes, including excess water and salts
Major Organs and Their Functions
Kidneys – the main organs of the excretory system
-- waste-laden blood enters the kidney and the kidney
filters out urea, excess
water and other waste
products, which eventually travel out of the kidney as
urine
-- eventually they travel through the ureter to the
urinary bladder
Rectum – solid (food) waste travels out of the body through
rectum
the
Skin – sweat glands remove excess water and salts from the
Lungs – expel the waste gas carbon dioxide
The Excretory System
body
The Respiratory System
Purpose: to provide the body with a fresh supply of oxygen for cellular respiration and
remove the waste product carbon dioxide
Major Organs and Their Functions
Nose – internal entry and exit point for air
Pharynx – serves as a passage way for both air and food at
throat
Larynx – your “voicebox”, as air passes over your vocal
speak
Trachea – the “windpipe”, or what connects your pharynx to
lungs
-- a piece of skin, called the epiglottis, covers the
swallow, preventing food from
entering
the back of the
chords, you
your
trachea when you
Bronchi – the two large passageways that lead from the trachea to your lungs (one for
each lung)
-- the bronchi are further subdivided into bronchioles
-- eventually, the further subdivisions lead to tiny air
sacs called alveoli
-- alveoli are in clusters, like grapes
-- capillaries surrounding each alveolus is where
exchange of gases with the blood occurs
The diaphragm is the muscle that causes you to breath
-- hiccups are involuntary contractions of the
diaphragm
the
Image of the Respiratory System
The Circulatory System
Purpose: to deliver oxygenated blood to the various cells and organ systems in your body
so they can undergo cellular respiration
Major Organs and Their Functions
Heart – the major muscle of the circulatory system
-- pumps blood through its four chambers (two ventricles and two atria)
-- pumps deoxygenated blood into the lungs, where it
gets oxygenated,
returned to the heart, and then
pumped out through the aorta to the rest of the
body
-- valve regulate the flow of blood between the chambers
Arteries – carry blood away from the heart and to the major organs of the body
Veins – carry blood back to the heart away from the major organs of the body
Capillaries – small blood vessels where gas exchange occurs
Blood – the cells that flow through the circulatory system
-- red blood cells contain hemoglobin, an iron-rich
oxygen
-- white blood cells function in the immune system
-- platelets help in blood clotting
Spleen – helps to filter out toxins in the blood
protein that carries
Image of the Circulatory System
The Nervous System
Purpose: to coordinate the body’s response to changes in its internal and external
environment
Major Organs and Their Functions
Brain – control center of the body, where all processes are relayed through
-- consists of cerebrum (controls though and senses)
(controls motor functions)
and cerebellum
Spinal Cord – sends instructions from the brain to the rest of the body and vice versa
-- any organism with a major nerve cord is classified as
Nerves – conduct impulses to muscle cells throughout the body
a chordate
Diagram of a Nerve Cell
The Endocrine System
Purpose: to control growth, development, metabolism and reproduction through the
production and secretion of hormones
Major Organs
-- hypothalamus
-- pituitary gland
-- thyroid
-- parathyroid
-- adrenal glands
-- pancreas
-- testes
-- ovaries
The Skeletal System
Purpose: to provide structure and support to the human body
Bones are where new blood cells are generated (in the marrow), and require the mineral
calcium for strength
Major Bones of the Human Body
-- femur (thigh bone)
-- humerus (upper arm)
-- radius and ulna (lower arm)
-- cranium (skull)
-- sternum (breastbone)
-- clavicle (shoulder blade)
-- fibula and tibia (calf)
-- vertebrae (back)
-- scalpula (shoulder)
-- pelvic bone
-- coccyx (tail bone)
-- phalanges (fingers/toes)
The Muscular System
Purpose: works with the skeletal and nervous system to produce movement, also helps to
circulate blood through the human body
-- muscle cells are fibrous
-- muscle contractions can be voluntary or involuntary
Major Muscles in the Human Body
-- biceps
-- triceps
-- glutes
-- hamstrings
-- deltoids
The Immune System
Purpose: to remove infectious diseases and other pathogens from the human body
Major Organs and Their Functions
Skin – also called the integumentary system, the skin is the body’s first line of defense
White Blood Cells – recognize disease agents (antigens) and create antibodies to tag and
remove these antigens
-- phagocytes are the white blood cell type that actually
these antigens
eats and destroys
Lymph Nodes – help restore fluid lost by the blood and return it to the circulatory system
Natural Selection & Artificial Selection
• Natural variation--differences among
individuals of a species
• Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Evolution by Natural Selection
• The Struggle for Existence-members of
each species have to compete for food,
shelter, other life necessities
• Survival of the Fittest-Some individuals
better suited for the environment
Struggle For Existence & Survival of
The Fittest
Natural Selection
• Over time, natural
selection results in
changes in inherited
characteristics of a
population. These
changes increase a
species fitness in its
environment
Descent
• Descent with Modification-Each living organism has
descended, with changes from other species over time
• Common Descent- were derived from common ancestors
Evidence of Evolution
• The Fossil Record
• Geographic Distribution of Living Things
• Homologous Body Structures
• Similarities in Early Development
Evidence for Evolution
• The Fossil RecordLayer show change
• Geographic
Distribution of Living
Things
• Homologous Body
Structures
• Similarities in Early
Development
Evidence of Evolution
• The Fossil Record
• Geographic
Distribution of Living
Things-similar
environments have
similar types of
organisms
• Homologous Body
Structures
• Similarities in Early
Development
Homologous Structures
• Homologous Structures-structures that
have different mature forms in different
organisms, but develop from the same
embryonic tissue
Evidence for Evolution
• Vestigial organs-organs that serve
no useful function in an organism
• i.e.) appendix, miniature legs, arms
Similarities in Early Development
Summary of Darwin’s Theory
• Individuals in nature differ from one another
• Organisms in nature produce more offspring
than can survive, and many of those who do
not survive do not reproduce.
Summary of Darwin’s Theory
• Because more organisms are produce than
can survive, each species must struggle for
resources
• Each organism is unique, each has advantages
and disadvantages in the struggle for
existence
Summary (cont.)
• Individuals best suited for the environment
survive and reproduce most successful
• Species change over time
Summary (cont.)
• Species alive today descended with modification
from species that lived in the past
• All organisms on earth are united into a single family
tree of life by common descent
Have you ever wondered how animals are able to
survive in the wild?
Animals have certain adaptations that help
them to survive.
Think about the way you dress in the winter.
You don’t wear your shorts and bathing suit when it’s snowing outside!
You wear warm clothes, and maybe even a
hat and mittens to protect yourself from
the weather.
The way you dress in the winter, as well as the way that you run and
hide from someone throwing snow at you are kinds of …
Adaptations.
We can separate adaptations into two categories:
A
D
Physical
A
P
T
AND
A
T
I
O
N
S
Behavioral
Physical adaptations
are body structures that allow an
animal to find and consume food,
defend itself, and to reproduce its
species.
Physical adaptations
help an animal survive in
its environment.
© A. Weinberg
Physical adaptation
Camouflage (use of color in a surrounding)
The chameleon can change its color to match its surroundings. Can you
do that?
Physical adaptation
Mimicry
(looking or sounding like another living organism)
The Viceroy butterfly uses mimicry to look like the Monarch butterfly.
Can you tell them apart?
I’m the Viceroy!
Not poisonous
Poisonous
I’m the Monarch!
Physical adaptation
Chemical defenses (like venom, ink, sprays)
Physical adaptations
Body coverings & parts (claws, beaks, feet, armor plates, skulls,
teeth)
The elephant’s trunk is a physical adaptation that helps it to clean
itself, eat, drink, and to pick things up.
Now let’s learn about
Behavioral Adaptations…
Behavioral Adaptations allow animals to
respond to life needs.
Behavioral Adaptations are animals’
actions.
Remember that Physical Adaptations are body
structures.
Each organism has unique methods of
adapting to its environment by means of
different actions.
We can divide Behavioral Adaptations into two groups:
Instinctive
Learned
These behaviors
happen naturally &
don’t have to be
learned.
These behaviors
must be taught.
Instinctive
behaviors
Methods of gathering &
storing food
Finding shelter
happen naturally & don’t
need to be learned
=
Defending oneself
Raising young
Hibernating
Migrating
Learned
behaviors
=
Obtained by interacting with
the environment and cannot
be passed on to the next
generation except by
teaching.
In this lesson, we have learned about
animal adaptations.
There are 2 ways to describe adaptations:
Physical
and
Behavioral
Nevada's Bioregions
Western Nevada:Transition zone from Sierra
Nevada bioregion to Great Basin cold desert.
Dominate plant species:
Single Leaf Pinion,
Rabbit Brush,
Utah Juniper,
Sage,
Native Grasses.
Eastern Nevada: Great Basin bioregion
Dominate animal species:
Larger Mammals: Feral
HorsesDescendants of domestic
European horses that have become wild
Featured on the Nevada State quarter
Herds are “managed” so that they don’t
destroy fragile rangeland
BearsThis bioregion is home to the
American Black Bear
Large and adaptable omnivore
Mountain LionThe largest predator of the
bioregion.
Great Basin Bioregion
Central / Eastern Nevada
Classified as a cold desert
Not as dry as the Mojave Desert
Tall mountain ranges provide
unique local climatesDominate
plant species: Utah
JuniperBerries are a food source
for birds
SingleleafPinionUsed by Native
Peoples and animals as a major
food source
Great Basin Bristlecone
PineBelieved to be the oldest
living organism on earth
Core samples of tree rings
confirm 2500 years old
Two Secrets of Survival: Energy Flow
and Matter Recycle
• An ecosystem
survives by a
combination of
energy flow and
matter recycling.
Figure 3-14
Condensation
Rain clouds
Transpiration
Precipitation
to land
Transpiration from
plants
Precipitation
Runoff
Surface runoff
(rapid)
Evaporation
Evaporation
from land
Precipitation
Evaporation
from ocean
Precipitation
to ocean
Surface
runoff
(rapid)
Infiltration and
Percolation
Groundwater movement (slow)
Ocean storage
Fig. 3-26, p. 72
Fig. 3-27, pp. 72-73
Effects of Human Activities
on Carbon Cycle
• We alter the carbon
cycle by adding
excess CO2 to the
atmosphere
through:
– Burning fossil fuels.
– Clearing vegetation
faster than it is
replaced.
Figure 3-28