Biology

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Terms in this set (...)

Scientific question
Questions that can be answered by using experiments and factual reasoning.
Biology
The study of living organisms and how they function.
Scientific Method
A method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.
Hypothesis
1st part of the scientific method
experimental design
Experimental design refers to how participants are allocated to the different conditions (or IV groups) in an experiment.
variable
factors that are kept constant or unchanging.
observation
The process of studying of something to gain information.
inference
A conclusion made up of facts and inferring knowledge.
conclusion
The final ending or idea of a process
prediction
A statement about the hypothesis
extrapolation
To or estimate by expanding know information
theory
An assumption based on limited information or something that hasn't yet been proved
constants
something thats unchanging
qualitative observations
detailed examination with your senses only
quantitative observations
measuring something with numbers
homeostasis
Balancing human or any living organisms
metabolism
The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life
heredity
The genetic transmission of characteristics from parent to offspring.
Golgi apparatus
packages proteins from the ER and materials and sends them to other parts of the cell
Smooth ER
network or tubular membranes within the cytoplasm of the cell with a smooth surface; functions in a variety of different metabolic processes such as synthesis of lipids, oils, phospholipid and steroids; process drugs, alcohol, and store calcium ions
Rough ER
network of tubular membanes within the cytoplasm of the cell with a rough surface (ribosomes are attached to it); helps the ribosomes make proteins, such as insulin
Organelles
tiny structures within the cell that carry out specific functions
plasma membrane
forms a flexible boundary between the living cell and its surroundings; made if phospholipids
nucleus
oval-shaped organelle that contains DNA and controls much of the cell's activities by directing protein synthesis
microfilament
actin filaments; solid rods of globular proteins
microtubule
straight, hollow tubes used for transportation; composed of globular proteins
mitochondrion
carries out cellular respiration; rod-shaped organelle that makes energy for the cell to function with; converts the energy stored in food to energy the cell can use (ATP); "powerhouse" of cell
nucleolus
nuclear subdomain that assembles ribosomal subunits in eukaryotic cells; makes rRNA to form the subunits of ribosomes, which then exit to the cytoplasm
chromatin
complex of DNA and proteins that form within the nucleus of eukaryotic cells; directs the cells' functions
vacuole
sac-like organelle that holds water, food and organisms; can also store waste products until removed
chloroplast
green structure that captures energy from sunlight and changes it to energy that cells can use in making food.
prokaryote
plant, bacteria or archea cell
eukaryote
animal cell with nucleus
plasmodesma
...
ribosomes
small grain-shaped organelle that produces proteins
cell membrane
thin, flexible barrier that surrounds the cell and controls what goes in and out; found in animal cells
cytoplasm
the thick fluid region of a cell inside the membrane or next to the nucleus
lysosome
membrane-enclosed sac of digestive enzymes; contains chemicals that break down bigger food particles so they can be used in the cell; also break down used cell parts. The cell's "recycling center".
cell wall
rigid layer surrounding the cells of plants
multicellular
made of many cells
unicellular
single-celled organism
centriole
small set of microtubules arranged in a specific way
phospholipid bilayer
thin membrane of lipid molecules
cytosol
part of cytoplasm not held by an organelle
cilia
the appendages that propel certain cells
extracellular matrix
helps hold cells together in tissues and protects and supports the plasma membrane. Made up of glycoproteins (proteins bonded with carbohydrates)
cytoskeleton
networks of protein fibers that extend through the cell
cell theory
all living things are composed of cells and all cells come from other cells
why are cells so small?
smaller cells have more surface area across which to pass oxygen, nutrients and waste materials
flagella
a projection from a prokaryotic cell that propels it through its liquid environment
cellular metabolism
chemical activities of cells
nuclear envelope
double membrane enclosing the nucleus; controls the flow of materials in and out of the nucleus
mRNA
messenger RNA that direct protein synthesis
where are ribosomes found?
free-floating in the cytosol, or bound to the rough ER or the nuclear envelope
endomembrane system
A system of membranes that are specific to a eukaryotic cell. Some are physically connected, while others link when vesicles transfer membrane segments between them.
vesicle
sacs made of membranes
what makes up the endomembrane system?
nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles and the plasma membrane.
What does the Golgi apparatus do?
processes, warehouses and ships (outside and inside cell) ER products
ATP
Adenine Triphosphate - main energy source for cellular work
stroma
...
thylakoids
...
Plant Cell
What type of cell is this?
Animal Cell
What type of cell is this?
X) cell wall
Which of the following is NOT a structure found in human cells:
W) mitochondrion
X) cell wall
Y) lysosome
Z) peroxisome
W) wing of a bat and the arm of a human
Which of the following are homologous structures:
W) wing of a bat and the arm of a human
X) leg of a cat and the wing of a fly
Y) stinger of a bee and the fang of a snake
Z) rattler of a rattle snake and the whistle of a song bird
Nucleus
What organelle functions to isolate a human cell's chromosomes from the cytoplasm?
Species
In the taxonomical name Homo sapiens, what taxonomical rank does 'sapiens' represent?
Cell
What is the basic unit of life?
Chloroplast
In what organelle of a plant cell does photosynthesis occur?
Z) ovary
In which of the following places would meiosis (cell division) most likely occur in a mammal:
W) skin
X) liver
Y) heart
Z) ovary
Y) glucose
Which of the following is the most common source of energy
for brain cells in humans:
W) nucleic acids
X) proteins
Y) glucose
Z) pectins
W) have no known function in their present owners
Vestigial structures:
W) have no known function in their present owners
X) function in an analogous fashion in species
Y) evolve homologously until functional
Z) control nervous system functions
Photosynthesis
It is generally believed that most of the oxygen in the air on Earth today came from what general biological process:
DNA
What is the most common term for the biological polymer found in chromosomes that stores genetic information?
Osmosis
The spontaneous movement of molecules through a semi-permeable membrane in order to create equilibrium.
Nucleus
These structures are located inside of a cell's...
Body Systems
Sets of organs in our bodies that do the work to keep us healthy and alive.
Atom
Tiniest part of all living and non-living things.
cells
Small part of all living things.
Molecules
Many cells working together.
Organs
Made of thousands of cells, connected by several body systems to do work to keep our bodies healthy & alive.
Kingdoms
Classifications of Living things.
Mammals
Living things with vertebra, hair or fur, gives birth to babies, feed the babies milk form their bodies & warm blooded.
Birds
May or may not fly, with vertebra, lay eggs, have feathers
Reptiles
Land & water animals, no vertebra, most lay eggs some have babies, smooth or rough scaly skin, no legs or arms.
Amphibians
Mostly water animals but can live on land, smooth or rough scaly skin, lay eggs & may have lungs.
Mollusks
Slimy animals, no skin or vertebra & no shells.
Arthropods
Hard body sections & no vertebra.
Worms
No vertebra, ears or eyes live underground & slimy.
Jellies
Have long electric tentacles, soft bodies & no vertebra.
Crustaceans
Shells soft bodies, no vertebra &Hard shells.
Fish
Gills & fins, cold blooded.
Insects
2 - 6 Legs, no vertebra, lay eggs, many eyes.
Arachnids
8 Legs, no vertebra, may have wings, lay eggs.
Marsupials
Mammals but with baby pouch on outside of bodies.
Plants
photosynthesis
Conversion of light energy from the sun into chemical energy.
products of photosynthesis are glucose and oxygen
photosynthesis equation(very important)
6CO2 + 6H2O --> light energy --> C6H12O6 + 6O2
chloroplasts
A structure in the cells of plants and some other organisms that captures energy from sunlight and uses it to produce food.
main function of chloroplasts is to produce food (glucose)
Chloroplasts contain the pigment, chlorophyll. Chlorophyll absorbs most of the colors in the color spectrum, and reflects only green and yellow wavelengths of light. This is why we see leaves as green or yellow - because these colors are reflected into our eyes.
glucose
another name for sugar C6H12O6
three things used for making glucose are sunlight water and carbon dioxide
used for energy and growth
sunlight
main source of energy
cellular respiration
C6H1206->CO2 + H20+ ENERGY (released)
goal is to create ATP
occurs in all living things
cell
mitochondria
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.
ATP
(adenosine triphosphate) main energy source that cells use for most of their work
the energy is stored in ATP until it is released by the reactions remove a phosphate from ATP
a simple way of remembering it is just that it's just energy
Metabolism
The sum total of all processes in an organism which convert energy and matter from outside sources and use that energy and matter to sustain the organism's life functions.
Anabolism
The sum total of all processes in an organism which use energy and simple chemical building blocks to produce large chemicals and structures necessary for life.
Catabolism
The sum total of all processes in an organism which break down chemicals to produce energy and simple chemical building blocks.
Photosynthesis
The process by which green plants and some other organisms use the energy of sunlight and simple chemicals to produce their own food.
Herbivores
Organisms that eat only plants.
Carnivores
Organisms that eat only organisms other than plants.
Omnivores
Organisms that eat both plants and other organisms.
Producers
Organisms that produce their own food.
Consumers
Organisms that eat living producers and/or other consumers for food.
Decomposers
Organisms that break down the dead remains of other organisms.
Autotrophs
Organisms that are able to make their own food.
Heterotrophs
Organisms that depend on other organisms for their food.
Receptors
Special structures that allow living organisms to sense the conditions of their internal or external environment.
Asexual reproduction
Reproduction accomplished by a single organism.
Sexual reproduction
Reproduction that requires two organisms
Inheritance
The process by which physical and biological characteristics are transmitted from the parent (or parents) to the offspring.
Mutation
An abrupt and marked change in the DNA of an organism compared to that of its parents
Hypothesis
An educated guess that attempts to explain an observation or answer a question.
Theory
A hypothesis that has been tested with a significant amount of data.
Scientific law
A theory that has been tested by and is consistent with generations of data.
Microorganisms
Living creatures that are too small to see with the naked eye.
Prokaryotic cell
A cell that has no distinct, membrane-bounded organelles.
Eukaryotic cell
A cell with distinct, membrane-bounded organelles.
Species
A unit of one or more populations of individuals that can reproduce under normal conditions, produce fertile offspring, and are reproductively isolated from other such units.
Taxonomy
The science of classifying organisms.
Binomial nomenclature
Naming an organism with its genus and species name.
Pathogen
An organism that causes disease.
Parasite
An organism that feeds on a living host.
Aerobic organism
An organism that requires oxygen.
Anaerobic organism
An organism that does not require oxygen.
Steady state
A state in which members of a population die as quickly as new members are born.
Exponential growth
Population growth that is unhindered because of the abundance of resources for an ever-increasing population.
Logistic growth
Population growth that is controlled by limited resources.
Conjugation
A temporary union of two organisms for the purpose of DNA transfer.
Endospore
The DNA and other essential parts of a bacterium coated with several hard layers.
Strains
Organisms from the same species that have markedly different traits.
Pseudopod
A temporary, foot-like extension of a cell, used for locomotion or engulfing food.
Nucleus
The region of a eukaryotic cell that contains the cell's main DNA.
Vacuole
A membrane-bounded "sac" within a cell.
Flagellate
A protozoan that propels itself with a flagellum.
Pellicle
A firm, flexible coating outside the plasma membrane.
Chloroplast
An organelle containing chlorophyll for photosynthesis.
Chlorophyll
A pigment necessary for photosynthesis.
Eyespot
A light-sensitive region in certain protozoa
Symbiosis
A close relationship between two or more species where at least one benefits.
Mutualism
A relationship between two or more organisms of different species where all benefit from the association.
Commensalism
A relationship between two organisms of different species where one benefits and the other is neither harmed nor benefited.
Parasitism
A relationship between two organisms of different species where one benefits and the other is harmed.
Cilia
Hairlike projections that extend from the plasma membrane and are used for locomotion.
Spore
A reproductive cell with a hard, protective coating.
Plankton
Tiny organisms that float in the water.
Zooplankton
Tiny floating organisms that are either small animals or protozoa.
Phytoplankton
Tiny floating photosynthetic organisms, primarily algae.
Cellulose
A substance (made of sugars) that is common in the cell walls of many organisms.
Holdfast
A special structure used by an organism to anchor itself.
Sessile colony
A colony that uses holdfasts to anchor itself to an object.
Extracellular digestion
Digestion that takes place outside of the cell.
Mycelium
The part of the fungus responsible for extracellular digestion and absorption of the digested food.
Hypha
A filament of fungal cells.
Rhizoid hypha
A hypha that is imbedded in the material on which the fungus grows.
Aerial hypha
A hypha that is not imbedded in the material upon which the fungus grows.
Chitin
A chemical that provides both toughness and flexibility.
Membrane
A thin covering of tissue.
Fermentation
The anaerobic breakdown of sugars into smaller molecules.
Zygote
The result of sexual reproduction when each parent contributes half of the DNA necessary for the offspring.
Atoms
The basic building blocks of matter.
Matter
Anything that has mass and takes up space.
Model
An explanation or representation of something that cannot be seen.
Element
A collection of atoms that all have the same number of protons.
Molecules
Chemicals that result from atoms linking together.
Diffusion
The random motion of molecules from an area of high concentration to an area of low concentration.
Concentration
A measurement of how much solute exists within a certain volume of solvent.
Semipermeable membrane
A membrane that allows some molecules to pass through but does not allow other molecules to pass through.
Osmosis
The tendency of a solvent to travel across a semipermeable membrane into areas of higher solute concentration.
Catalyst
A substance that alters the speed of a chemical reaction but is not used up in the process.
Organic Molecule
A molecule that contains only carbon and any of the following: hydrogen, oxygen, nitrogen, sulfur, and/or phosphorous.
Biosynthesis
The process by which living organisms produce larger molecules from smaller ones.
Isomers
Two different molecules that have the same chemical formula.
Monosaccharides
Simple carbohydrates that contain 3 to 10 carbon atoms.
Disaccharides
Carbohydrates that are made up of two monosaccharides.
Polysaccharides
Carbohydrates that are made up of more than two monosaccharides.
Dehydration reaction
A chemical reaction in which molecules combine by removing water.
Hydrolysis
Breaking down complex molecules by the chemical addition of water.
Hydrophobic
Lacking any affinity to water.
Saturated fat
A lipid made from fatty acids that have no double bonds between carbon atoms.
Unsaturated fat
A lipid made from fatty acids that have at least one double bond between carbon atoms.
Peptide bond
A bond that links amino acids together in a protein.
Hydrogen bond
A strong attraction between hydrogen atoms and certain other atoms (usually oxygen or nitrogen) in specific molecules.
Respiration
The breakdown of food molecules with a release of energy.
Excretion
The removal of soluble waste materials.
Secretion
The release of biosynthesized substances.
Homeostasis
Maintaining stable internal conditions
Reproduction
Producing more cells.
Cytology
The study of cells.
Cell Wall
A rigid structure on the outside of certain cells, usually plant and bacteria cells.
Plasma membrane
The semipermeable membrane between the contents and either the cell wall or the cell's surroundings.
Cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended.
Ions
Substances in which at least one atom has an imbalance of protons and electrons.
Cytoplasmic streaming
The motion of cytoplasm in a cell that results in a coordinated movement of the cell's contents.
Mitochondria
The organelles in which nutrients are converted to energy.
Lysosome
The organelle in animal cells responsible for hydrolysis reactions that break down proteins, polysaccharides, disaccharides, and some lipids.
Ribosomes
Non-membrane-bounded organelles responsible fore protein synthesis.
Endoplasmic reticulum
An organelle composed of an extensive network of folded membranes that performs several tasks within a cell.
Rough ER
ER that is dotted with ribosomes.
Smooth ER
ER that has no ribosomes.
Central vacuole
A large vacuole that rests at the center of most plant cells and is filled with a solution that contains a high concentration of solutes.
Waste vacuoles
Vacuoles that contain the wast products of digestion.
Phagocytosis
The process by which a cell engulfs foreign substances or other cells.
Golgi bodies
The organelles where proteins and lipids are stored and then modified to suit the needs of the cell.
Microtubules
Spiral strands of protein molecules that form a tubelike structure.
Nuclear membrane
A highly-porous membrane that separates the nucleus from the cytoplasm.
Chromatin
Clusters of DNA, RNA, and proteins in the nucleus of a cell.
Cytoskeleton
A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement.
Microfilaments
Fine, threadlike proteins found in a cell's cytoskeleton.
Intermediate filaments
Threadlike proteins in the cell's cytoskeleton that are roughly twice as thick as microfilaments.
Phospholipid
A lipid in which one of the fatty acid molecules has been replaced by a molecule that contains a phosphate group.
Passive transport
Movement of molecules through the plasma membrane according to the dictates of osmosis or diffusion.
Active transport
Movement of molecules through the plasma membrane (typically opposite the dictates of osmosis or diffusion) aided by a process that requires energy.
Isotonic solution
A solution in which the concentration of solutes is essentially equal to that of the cell which resides in a solution.
Hypertonic solution
A solution in which the concentration of solutes is greater than that of the cell that resides in the solution.
Plasmolysis
Collapse of a walled cell's cytoplasm due to a lack of water.
Hypotonic solution
A solution in which the concentration of solutes is less than that of the cell that resides in the solution.
Activation energy
Energy necessary to get a chemical reaction going.
Genetics
The science that studies how characteristics get passed from parent to offspring.
Genetic factors
The general guideline of traits determined by a person's DNA.
Gene
A section of DNA that codes for the production of a protein of a portion of protein, thereby causing a trait.
Messenger RNA
The RNA that performs transcription.
Anticodon
A three-nucleotide base sequence on tRNA.
Codon
A sequence of three nucleotide bases on mRNA that refers to a specific amino acid.
Chromosome
DNA coiled around and supported by proteins, found in the nucleus of the cell.
Mitosis
A process of asexual reproduction in eukaryotic cells.
Interphase
The time interval between cellular reproduction.
Mother cell
A cell ready to begin reproduction, containing duplicated DNA and centrioles.
Centromere
The region that joins two sister chromatids.
Karyotype
The figure produced when the chomosomes of species during metaphase are arranged according to their homologous pairs.
Diploid cell
A cell with chromosomes that come in homologous pairs.
Haploid cell
A cell that has only one representative of each chromosome pair.
Diploid number (2n)
The total number of chromosomes in a diploid cell.
Haploid number (n)
the number of homologous pairs in a diploid cell.
Meiosis
The process by which a diploid (2n) cell forms gametes (n).
Gametes
Haploid cells (n) produced by diploid cells (2n) for the purpose of sexual reproduction.
Virus
A non-cellular infectious agent that has two characteristics: (1) It has genetic material (RNA or DNA) inside a protective protein coat. (2) It cannot reproduce on its own.
Antibodies
Specialized proteins that aid in destroying infectious agents.
Vaccine
A weakened or inactive version of a pathogen that stimulates the body's production of antibodies which can aid in destroying the pathogen.
DNA
Deoxyriboneucleic acid found mainly in the nucleus
replication
double the chromosomes
nucleotides
neuclic acid base pairs
RNA
receives instructions from DNA
Transcription
process of forming a neucleic acid using a template
Translation
uses the codons in mRNA to make a specific amino acid
proteins
monomers of amino acid chains
mitosis, meiosis
body cell reproduction and sex cell reproduction
sexual reproduction
2 parents male and female
asexual reproduction
1 parent
genes
segment of dna that codes for a specific trait
Chromosomes
made up of DNA and proteins
homeostasis
state reaches when each part of the body functions in equilibrium with other parts.
egg cell
also called ovum; female gamete
embryo
an organism in its early stages of development, especially before it has reaches a distinctively recognizable form.
fertilization
a process that occurs when the sperm and egg combine to produce an embryo
radiometric dating
a method used to determine the age of rocks using the decay of radioactive isotopes present in rocks.
carbon dating
used to tell the age of organic materials.
homologous structure
perform different functions in the species living in the different environment, or it may gave the same origin but different functions
analogous structure
have similar functions but different origin
divergent evolution
splitting of an ancestral population into two or more subpopulations that are geographically isolated from one another.
convergent evolution
analogous structure of unrelated organisms from different ancestors develop similar function such as butterfly wings and bird wings.
convergence
is an increase similarities among species derived from different ancestors as a result of similar adaptation to similar environment.
Theory of Use and Disuse
organs not in use will disappear while organs in use will develop.
Variation
differences in traits of organisms in a population
Theory of Evolution
states that evolutionary change comes through the production of variation in each generation and differential survival of individuals with different combinations of these variable characters.
amino acids
the building blocks of protein
anticodon
the complement of mRNA; triplet code on the tRNA
chromosomal mutations
changes in the chromosomes where parts of the chromosomes are broken and lost during mitosis
codon
each set of three nitrogenous bases in mRNA representing an amino acid or start/stop signal
genetic code
set of rules that specify to the codons in DNA or RNA that corresponds to the amino acids in proteins
nitrogenous base
is a carbon ring structure that contains one or more atoms of nitrogen. In DNA, Adenine, Thymine, Cytosine, Guanine.
mutation
any change in the DNA sequence
mRNA
messenger RNA, brings information from the DNA in the nucleus to the cytoplasm
rRNA
ribosomal rna, hold tightly to the mRNA and use its information to assemble amino acids
tRNA
transfer RNA, a type of RNA that attach the correct amino acid to the protein chain that is being synthesized in the ribosomes.
Recombinant DNA
A form of DNA produced by combining two genetic material from two or more different sources by means of genetic engineering
Transcription
process of copying DNA sequence into RNA
Translation
process of converting information in mRNA into a sequence of amino acids in a protein
accessory pigments
energy absorbing plant pigments other than chlorophyll
metabolism
all chemical processes that synthesize or break down materials within an organism.
PATHOGEN
MICROORGANISM THAT CAUSES ILLNESS OR DISEASE
BACTERIA
Bacteria are living cells and can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill.
BACTERIA GET IN BETWEEN CELLS
VIRUSES
Viruses can only reproduce inside host cells, and they damage the cell when they do this
VIRUSES GET INTO CELL
DISEASES CAUSED BY VIRUSES
influenza - flu, colds, Measles, mumps, rubella, chicken pox, AIDS
DISEASES CAUSED BY BACTERIA
food poisoning, Cholera, typhoid, whooping cough,
gonorrhoea - a sexually transmitted disease
WHAT ARE BODY'S DEFENSE MECHANISMS?
SKIN, STOMACH ACID, EYELASHES, TEARS, COUGH
DEPENDENT VARIABLE
WHAT YOU MEASURE- ON Y AXIS
INDEPENDENT VARIABLE
WHAT YOU CHOOSE VALUES FOR- ON Y AXIS
CONTROL VARIABLE
VARIABLES THAT REMAIN CONSTANT OR UNCHANGED
ecology
the branch of biology that studies the interactions of organisms with one another and with nonliving parts of their environment
gene
sections of chromosomes made of DNA that code for traits. The basic unit of heredity.
genome
the complete genetic material contained in an individual.
heredity
the passing of traits from parent to offspring. Ex. scientists know that _____ can increase chances for certain diseases.
interdependence
organisms in a biological community live and interact with other organisms.
mutation
a change in the DNA of a gene.
natural selection
process in which organisms with favorable genes are more likely to survive to reproduce. Ex. the idea of ____ ______ was first presented by Charles Darwin.
organism
any living thing; something that meets all criteria of life. Ex. so far, we have not found proof of any living ________ on another planet.
pH
a relative measure of the hydrogen ion concentration within a solution; Latin for "probably hydrogens".
differentiation
process by which cells become specialized for specific functions.
excretion
removal of metabolic waste.
ingestion
taking in food from the environment.
regulation
process by which organisms maintain homeostasis, a stable internal environment.
reproduction
process by which organisms produce new organisms of their own kind
respiration
release of chemical energy from certain nutrients.
synthesis
chemical combination of simple substances to form complex substances.
DNA
nucleic acid polymer that stores genetic information.
equilibrium
the state of both sides are balanced
evolution
the process of change that has transformed life on Earth
theory
a system of ideas that explains many related observations and is supported by a large body of evidence acquired through scientific investigation
species
group of similar organisms that can breed and produce fertile offspring. Ex. there are thousands of different ______ of butterflies.
matter
the material that everything in the universe is made of, including solids, liquids, and gases
element
a substance that cannot be broken down to other substances by chemical reactions. Ex. carbon is an essential ________ of life.
compound
a substance consisting of 2 or more elements in a fixed ratio. Ex. water is the most common _______ on Earth.
bacteria
a very small living things. Ex. Although some cause illness or disease, many ______ are harmless.
virus
a very small living thing that causes infectious illnesses. Ex. HIV is the _____ that causes AIDS.
algae
a very simple plant without stems or leaves that grows in or near water.
fungi
simple type of plant that has no leaves or flowers and that grows on plants or other surfaces. Ex. mushrooms are a _____.
oxygen
a gas that has no color or smell, is present in air, and is necessary for most animals and plants to live. Ex. the chemical symbol for _____ is O.

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