th
7
grade Life Science
– MCAS review
Cell Theory
• Cell - A cell is the smallest unit that is
capable of performing life functions.
• All living things are made up of cells.
• All cells come from preexisting cells
through cell division.
• There are two types of cells:
1) Prokaryotic
2) Eukaryotic
Prokaryotic
• Do not have
structures
surrounded by
membranes
• Few internal
structures
• One-celled
organisms,
Bacteria
Eukaryotic
• Contain organelles surrounded by membranes
• Most living organisms
Plant
Animal
“Typical” Animal Cell
“Typical” Plant Cell
Cell Membrane
• Outer membrane of cell
that controls movement
in and out of the cell
• Double layer
Cell Wall
• Most commonly found in
plant cells & bacteria
• Supports & protects cells
Nucleus
• Directs cell activities
• Separated from cytoplasm
by nuclear membrane
• Contains genetic material DNA
Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
Chromosomes
• In nucleus
• Made of DNA
• Contain instructions for
traits & characteristics
Cytoplasm
• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material
Endoplasmic Reticulum
• Moves materials around in cell
• Smooth type: lacks ribosomes
• Rough type (pictured):
ribosomes embedded in
surface
Ribosomes
• Each cell contains thousands
• Make proteins
• Found on endoplasmic
reticulum & floating throughout
the cell
Mitochondria
• Produces energy through
chemical reactions –
breaking down fats &
carbohydrates
• Controls level of water and
other materials in cell
• Recycles and decomposes
proteins, fats, and
carbohydrates
Golgi Bodies
• Protein 'packaging plant'
• Move materials within the cell
• Move materials out of the cell
Lysosome
• Digestive 'plant' for proteins, fats,
and carbohydrates
• Transports undigested material to
cell membrane for removal
• Cell breaks down if lysosome
explodes
Vacuoles
• Membrane-bound sacs for
storage, digestion, and waste
removal
• Contains water solution
• Help plants maintain shape
Chloroplast
• Usually found in plant cells
• Contains green chlorophyll
• Where photosynthesis takes
place
6 Kingdom Proposal
Archebacteria
EUbacteria
Cilia & Flagella
• Provide mobility
• Cilia
– Short, hair-like
– Used to move
substances outside
human cells
• Flagella
– Whip-like extensions
– Found on sperm cells
Passive Transport
• No energy required
• Move due to gradient
– differences in concentration, pressure, charge
• Move to equalize gradient
– High moves toward low
• There are several types of passive
transport:
1. Diffusion
2. Osmosis
Diffusion
• Molecules move to equalize concentration
Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water
– Into cell
– Out of cell
Active Transport
• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump
Photosynthesis
Photosynthesis is the
process in which carbon
dioxide (CO2) and water
(H2O) are used to
produce carbohydrates
and evolve oxygen (O2)
in the presence of light
and chlorophyll; the net
result is light energy
(radiant energy) is
converted into chemical
energy in the form of
fixed carbon compounds
(carbohydrates).
Respiratory System
Circulatory System
Digestive System
Muscular System
Skeletal System
Digestive System
Respiratory System
Circulatory
System
Muscular System
Protection, Support and Locomotion
The muscular system works to
make something move as muscles
contract.
The main tissue of the muscular system

muscle
There are 3 types of muscles
•
•
•
smooth muscle
cardiac muscle
skeletal muscle
The muscular system works closely with the
skeletal system, the nervous system and the
endocrine system.
Muscular System
Muscles
Smooth muscles - line internal tissues like
the esophagus and intestines - involuntary
Involuntary means you cannot control these
muscles. They work automatically.
They squeeze in a process called
peristalsis.
Cardiac muscles – make up
the heart – also involuntary
Cardiac muscles are also part of the circulatory system.
Muscular System
Skeletal muscles - attached to the bones of
the skeleton - voluntary
Skeletal muscles usually work in opposing pairs.
For example,
the biceps muscle bends the arm, and
the triceps muscle straightens the arm.
Biceps
Triceps
Skeletal
System
Ligaments
• tough connective tissue
• connects bones to bones
Tendons
• connects bones to muscles
Cartilage
• tough connective tissue
• covers the ends of bones at
movable joints
• also makes up your nose
and ears
Skeletal System
Protection, Support and Locomotion
The skeletal system provides a framework for the body.
Tissues of the skeletal system




bones,
ligaments,
tendons and
cartilage
Functions of bones:
 Protects the internal organs
 Allows muscles to move the body
 Produces red blood cells, white
blood cells and platelets
 Stores minerals like calcium
Vertebrate organisms have skeletal systems.
Watson & Crick proposed…
•DNA (Deoxyribonucleic Acid) had
specific pairing between the
nitrogen bases:
ADENINE – THYMINE
CYTOSINE - GUANINE
•DNA was made of 2 long stands of
nucleotides arranged in a specific
way.
The Code of Life…
• The “code” of the chromosome is the
SPECIFIC ORDER that bases occur.
A T C G T A T G C G G…
DNA Double Helix
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone
DNA Double Helix
5
O
3
3
P
5
O
O
C
G
1
P
5
3
2
4
4
2
3
P
1
T
5
A
3
P
O
O
P
5
O
3
5
P
DNA is wrapped tightly around
histones and coiled tightly to form
chromosomes
DNA Replication
• DNA must be copied
• The DNA molecule
produces 2 IDENTICAL
new complementary
strands following the rules
of base pairing:
A-T, G-C
•Each strand of the
original DNA serves as a
template for the new
strand
DNA Transcription
• DNA can “unzip”
itself and RNA
nucleotides match
up to the DNA
strand. See p.301
• Both DNA & RNA
are formed from
NUCLEOTIDES and
are called NUCLEIC
acids.
AMAZING DNA FACTS…
• DNA from a single human
cell extends in a single
thread for almost 2 meters
long!!!
• It contains information
equal to some 600,000
printed pages of 500 words
each!!!
(a library of about 1,000 books)
Mitosis
Meiosis
Meiosis
Based on the diagram,
The difference between mitosis and meiosis is
that mitosis produces two identical daughter
cells and meiosis produces four genetically
different daughter cells
Mitosis
Parent cell
Diploid (2n)
Meiosis
Parent cell
Diploid (2n)
1st division
Diploid (2n)
Daughter cell
Diploid (2n)
1st division
Diploid (2n)
2nd division
Daughter cell
Haploid (n)
2nd division
Daughter cell
Haploid (n)
2nd division
Daughter cell
Haploid (n)
2nd division
Daughter cell
Haploid (n)
Daughter cell
Diploid (2n)
The numbers
• The cells created from mitosis are diploid or 2n.
• The cells created from meiosis are haploid or n
Definitions:
• Diploid (2n) – two of each type of chromosome
(in homologous pair – carry the same trait)
• Haploid (n) – one of each type of chromosome
Let’s try it…
• Human cells have 46 chromosomes.
• Therefore, the diploid number (2n) of
chromosomes in humans is 46.
• The haploid number (n) of chromosomes in
humans is 23.
The reason why: mitosis
• To replace other cells that have been damaged
or worn out
• To allow multicellular organisms to grow
• For asexual reproduction
• Because they get too big!
The reason why: meiosis
• Meiosis results in four cells with half the
number of chromosomes so that when the
sex cells (sperm and egg) combine, the
original or normal number of chromosomes
will be restored
• Mitosis occurs in normal body cells (i.e. skin
cells), and meiosis occurs in sex cells (i.e.
sperm and egg) only.
Sexual vs. Asexual Reproduction
Type of Reproduction
Sexual
Methods
Disadvantages
Internal fertilization
Diversity in offspring
External fertilization
Offspring less likely to
have mutations show
up
Population increases are
limited
Can increase
populations rapidly
Lack of diversity in
offspring
Does not require a mate
for reproduction to take
place
Because they reproduce
offspring genetically
identical to parents, the
offspring inherit any
mutations of the parent.
Conjugation
Budding
Asexual
Advantages
Requires a mate to
reproduce
Spores
Fission
Father of Genetics
 Monk and teacher.
 Experimented with purebred tall and short
peas.
 Discovered some of the basic laws of
heredity.
 Studied seven purebred traits in peas.
 Called the stronger hereditary factor
dominant.
 Called the weaker hereditary factor
recessive.
 Presentation to the Science Society
in1866 went unnoticed.
 He died in 1884 with his work still
unnoticed.
 His work rediscovered in 1900.
 Known as the “Father of Genetics”.
Mendel’s Observations
 He noticed that peas are easy to breed for
pure traits and he called the pure strains
purebreds.
 He developed pure strains of peas for seven
different traits (i.e. tall or short, round or
wrinkled, yellow or green, etc.)
 He crossed these pure strains to produce
hybrids.
 He crossed thousands of plants and kept
careful records for eight years.
Mendel’s Peas
 In peas many traits appear in two forms (i.e. tall
or short, round or wrinkled, yellow or green.)
 The flower is the reproductive organ and the
male and female are both in the same flower.
 He crossed pure strains by putting the pollen
(male gamete) from one purebred pea plant on
the pistil (female sex organ) of another purebred
pea plant to form a hybrid or crossbred.
Mendel’s Results
Mendel crossed purebred tall plants with
purebred short plants and the first
generation plants were all tall.
When these tall offspring were crossed
the result was a ratio of 3 tall to 1 short.
Mendel’s Peas
Mendel’s Experiments
 He experimentally
crosses different
strains to develop
hybrids.
 He then crossed
the hybrids and
analyzed the
results.
Dominant Traits RULE
• Strong Hereditary
traits cover weak
traits.
• Mendal called
stronger traits
– DOMINANT
• Mendal called weaker
traits
– recessive
• Dominant traits are
represented by capital
letters (T) while recessive
traits are represented by
lower case letters (t). try
and follow the diagram on
the next slide while
keeping the DOMINANT
and recessive letters in
mind. ( TT) (tt )
Mr. & Mrs. Skelton Eye Color
Darwin’s Theories
• Evolution, or change over time, is the process
by which modern organisms have descended
from ancient organisms.
• A scientific theory is a well-supported testable
explanation of phenomena that have occurred in
the natural world.
• 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.
Darwin’s Theories
(Continued)
• 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
• Over time, natural selection results in
changes in inherited characteristics of a
population. These changes increase a
species fitness in its environment
Evidence for Evolution
• The Fossil RecordLayer show change
• Geographic
Distribution of Living
Things
• Homologous Body
Structures
• Similarities in Early
Development
Homologous Structures
• Homologous
Structuresstructures that
have different
mature forms in
different
organisms, but
develop from the
same embryonic
tissue
Similarities in Early
Development
Autotrophs
• A groups of organisms that can use the energy
in sunlight to convert water and carbon dioxide
into Glucose (food)
• Autotrophs are also called Producers because
they produce all of the food that heterotrophs
use
• Without autotrophs, there would be no life on
this planet
• Ex. Plants and Algae
Autotrophs
• Chemotrophs
– Autotrophs that get their energy from inorganic
substances, such as salt
– Live deep down in the ocean where there is no
sunlight
– Ex. Bacteria and Deep Sea Worms
Heterotrophs
• Organisms that do not make their own food
• Another term for Heterotroph is consumer
because they consume other organisms in order
to live
• Ex. Rabbits, Deer, Mushrooms
Heterotrophs
• Consumers
– 1. Scavengers/Detritivores – feed on the
tissue of dead organisms (both plants and
animals) Ex. – Vultures, Crows, and Shrimp
– 2. Herbivores – eat ONLY plants
• Ex. – Cows, Elephants, Giraffes
– 3. Carnivores – eat ONLY meat
• Ex. – Lions, Tigers, Sharks
– 4. Omnivores – eat BOTH plants and
animals Ex. – Bears and Humans
– 5. Decomposers – absorb any dead
material and break it down into simple
nutrients or fertilizers
• Ex. – Bacteria and Mushrooms
Food Chains
• The energy flow from one trophic level to the
other is know as a food chain
• A food chain is simple and direct
• It involves one organism at each trophic level
–
–
–
–
Primary Consumers – eat autotrophs (producers)
Secondary Consumers – eat the primary consumers
Tertiary Consumers – eat the secondary consumers
Decomposers – bacteria and fungi that break down
dead organisms and recycle the material back into the
environment
Food Chain
Food Web
• Notice that
the direction
the arrow
points  the
arrow points
in the
direction of
the energy
transfer, NOT
“what ate
what”
Food Web
Symbiosis
• A close and permanent association between
organisms of different species
– Commensalism – a relationship in which one
organism benefits and the other is not affected
• Example: Barnacles on a whale
– Mutualism – a relationship in which both organisms
benefit from each other
• Example: Birds eating pest off a rhino’s back
– Parasitism – A relationship in which one organism
benefits and the other is harmed
• Example: Ticks on a dog
Ecological Succession
• A change in the community in which new
populations of organisms gradually replace
existing ones
1. Primary Succession – occurs in an area where
there is no existing communities and for some reason
(s) a new community of organisms move into the area
2. Secondary Succession – occurs in an area where
an existing community is partially damaged
3. Climax Community – a community that is stable
and has a great diversity of organisms