7th grade Life Science

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7th grade Life Science MCAS review
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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

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Prokaryotic

• Do not have structures surrounded by membranes
• Few internal structures
• One-celled organisms, Bacteria

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Eukaryotic

• Contain organelles surrounded by membranes
• Most living organisms

Plant
Animal
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Typical Animal Cell
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Typical Plant Cell
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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

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Nucleus

• Directs cell activities
• Separated from cytoplasm by nuclear membrane
• Contains genetic material - DNA

Nucleolus

• Inside nucleus
• Contains RNA to build proteins

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Chromosomes

• In nucleus
• Made of DNA
• Contain instructions for traits characteristics
  

Cytoplasm

• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material

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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

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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

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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

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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

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6 Kingdom Proposal
Archebacteria
EUbacteria
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(No Transcript)
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(No Transcript)
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King Philip Came Over For Gold Specks or Keep
Phones Clean or Fungus Grows Swiftly
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Cilia Flagella

• Provide mobility
• Cilia
• Short, hair-like
• Used to move substances outside human cells
• Flagella
• Whip-like extensions
• Found on sperm cells

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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

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Diffusion

• Molecules move to equalize concentration

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Osmosis

• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water
• Into cell
• Out of cell

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Active Transport

• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump

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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).  
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Respiratory System
Circulatory System
Digestive System
Muscular System
Skeletal System
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Digestive System
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Respiratory System
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Circulatory System
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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.
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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.
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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.
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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

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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.
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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.

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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

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DNA Double Helix

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DNA Double Helix

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DNA is wrapped tightly around histones and coiled
tightly to form chromosomes
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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

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DNA Transcription

• DNA can unzip itself and RNA nucleotides match
  up to the DNA strand.
• Both DNA RNA are formed from NUCLEOTIDES and
  are called NUCLEIC acids.

See p.301
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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)

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Meiosis
Mitosis
Meiosis
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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

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Mitosis
Meiosis
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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

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Lets 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.

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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!

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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.

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Sexual vs. Asexual Reproduction
Type of Reproduction Methods Advantages Disadvantages
Sexual Internal fertilization Diversity in offspring Offspring less likely to have mutations show up Requires a mate to reproduce Population increases are limited
Sexual External fertilization Diversity in offspring Offspring less likely to have mutations show up Requires a mate to reproduce Population increases are limited
Sexual Conjugation Diversity in offspring Offspring less likely to have mutations show up Requires a mate to reproduce Population increases are limited
Asexual Budding Can increase populations rapidly Does not require a mate for reproduction to take place Lack of diversity in offspring Because they reproduce offspring genetically identical to parents, the offspring inherit any mutations of the parent.
Asexual Spores Can increase populations rapidly Does not require a mate for reproduction to take place Lack of diversity in offspring Because they reproduce offspring genetically identical to parents, the offspring inherit any mutations of the parent.
Asexual Fission Can increase populations rapidly Does not require a mate for reproduction to take place Lack of diversity in offspring Because they reproduce offspring genetically identical to parents, the offspring inherit any mutations of the parent.
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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.

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Mendels 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.

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Mendels 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.

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Mendels 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.
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Mendels Peas
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Mendels Experiments

• He experimentally crosses different strains to
  develop hybrids.
• He then crossed the hybrids and analyzed the
  results.

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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 )

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Mr. Mrs. Skelton Eye Color
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Darwins 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.

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Darwins 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

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Evidence for Evolution

• The Fossil Record-Layer show change
• Geographic Distribution of Living Things
• Homologous Body Structures
• Similarities in Early Development

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Homologous Structures

• Homologous Structures-structures that have
  different mature forms in different organisms,
  but develop from the same embryonic tissue

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Similarities in Early Development
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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

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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

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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

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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

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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

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Food Chain
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Food Web

• Notice that the direction the arrow points ? the
  arrow points in the direction of the energy
  transfer, NOT what ate what

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Food Web
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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 rhinos back
• Parasitism A relationship in which one organism
  benefits and the other is harmed
• Example Ticks on a dog

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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