Science Section Flashcards
What is a cell?
A cell is the smallest living functional unit of an organism.
What are cells composed of?
Living cells are
composed of approximately 60% water and vary in size and shape.
How is a red blood cell shaped?
Disc shaped. Biconcave discs.
how is a nerve cell shaped?
whereas nerve cells can be very long and have extensions on their main
body.
What does the nucleus do?
The nucleus contains the genetic information, or DNA (deoxyribonucleic acid), and controls
the activities of the cell.
What is the plasma cell membrane?
The plasma (or cell) membrane is known as a semipermeable membrane that separates the contents of the cell from the surrounding fluid
What does the interstitial fluid contain?
The interstitial fluid contains substances such as amino acids, sugars, fatty acids,
hormones, neurotransmitters, and salts
What does selectively permeable mean?
The term, selectively permeable (semipermeable),
refers to the selective nature of the plasma membrane. It contains pores and channels that
allow only particles of the right size or the right chemical nature to pass through. Additionally,
the plasma membrane contains receptors that bind with specific substances, thus allowing for
special entry or signals the cell to perform a certain activity.
What is the cytoplasm?
The cytoplasm is the fluid matrix found between the plasma membrane and the nucleus that
acts as scaffolding for the organelles.
What are the organelles
Organelles, or “little organs,” are specialized units in the
cell that perform certain functions.
What are the mitochondria?
The mitochondria are the locations for cellular respiration
or the conversion of food to energy at the cellular level. Thus the mitochondria are the sites of
energy production and of most of its ATP (adenosine triphosphate), which is a chemical the
cell uses to store and transfer energy within itself
What are ribosomes?
Ribosomes are the sites of protein
synthesis in the cell.
What does the rough ER do?
Rough ER, named for the fact that it has ribosomes on its surface,
serves to store and deliver the proteins made by the attached ribosomes.
What does the smooth ER do?
Smooth ER is free of
ribosomes and is found in a variety of cells. It performs varying functions in different cells,
including the storage of enzymes and minerals and the folding of proteins. It is thought to be
involved in the detoxification of chemicals and the metabolism of fats.
What does the golgi complex do?
The Golgi complex
modifies and packages proteins destined for use in the cell or for export from the cell.
What do lysosomes do?
Lysosomes are sacs that contain strong digestive enzymes. These sacs are responsible for
digesting waste and cell structures that are malfunctioning or dead.
How can plant cells be distinguished from animal cells?
Plant cells can be distinguished from animal plants by the presence of a surrounding cell wall
and chloroplasts.
What does the cell wall do?
The cell wall is essential for protection of the cell, the maintenance of the
shape, and water balance.
What are chloroplasts?
Chloroplasts contain chlorophyll, which is necessary for
photosynthesis
What are vacuoles?
Plant cells also often have large vacuoles, which are compartments in the
cytoplasm that act as places for secretion, excretion, and storage
Why do cells divide?
Cells divide for a number of reasons: growth, repair, and the production of gametes (sperm or
egg cells).
What is the most important part of cell division?
The most important result of cell division is that the genetic material, DNA, is
transmitted to the offspring.
What is chromatin?
When a cell is not dividing, DNA is found in the form of loosely structured
chromatin,
What is chromosomes?
but when a cell is dividing, the DNA is seen in condensed rod-shaped bodies
called chromosomes.
What is mitosis?
When cells divide, the appropriate amount of genetic material must be passed on to the new
daughter cells. In somatic (non-reproductive) cells, the new cells are identical copies of the
parent cells. This is achieved by a doubling of the chromosomes prior to division. This type of
cell division is referred to as mitosis, and it is useful in the growth and repair of our bodies.
What are gametes?
These reproductive cells contain half
of the normal number of chromosomes so that the zygote, the cell created by the union of a
sperm and egg, contains a full set of chromosomes, half from each parent.
What is meiosis?
This type of
division, or meiosis, consists first of a doubling of chromosomes and then two subsequent
divisions. Thus the products are four daughter cells, each with half the normal number of
chromosomes.
What is an organ?
Various tissues are combined into an organ, which performs a specialized function in the
body
What are the types of muscle tissues?
(skeletal, cardiac, and smooth)
What are the types of nervous tissue?
Neurons
What are the types of epithelial tissue?
(skin, the lining of organs)
What are the types of connective tissue?
(cartilage, blood, fat, bone)
What is an organ system?
organ system, which is made up of a number of organs
working together to carry out a major function
What is an organism?
The highest level of organization is the organism itself, such as the human body.
What is evolution?
In 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection,
which presented evidence for evolution, a theory regarding the processes that have produced
the biological diversity we see today
What is natural selection?
. evolution occurs by means of natural selection, the process by which the traits that
promote or enhance an organism’s ability to survive and reproduce are passed on to
following generations.
What is adaption?
In this struggle, the individuals best suited to their environment survive (“survival of the fittest”)
and pass on those traits to their offspring. This is called adaptation, the evolutionary process
of an organism to survive in a given environment.
Why does natural selection occur?
For natural selection to occur, organisms must have variations, some of which give the
individuals having them an advantage in the struggle for survival. The struggle for survival
occurs because each generation of a species produces more offspring than can survive.
What is the fossil record?
There is evidence supporting the theory of evolution, such as the fossil record, which consists
of remnants or traces of organisms from past geologic ages
What are vertebraes?
vertebrates (animals with backbones)
What is biogeography ?
(the geographical distribution of plants and animals),
What is comparative anatomy?
The comparison of organisms structures.
What is comparative embryology? the comparison of organisms’ embryos
the comparison of organisms’ embryos
What is molecular biology?
Biology at the molecular level
What is taxonomy?
In taxonomy (the study of scientific classification), taxonomists group species according to their similarities and differences. They are classified in a hierarchical system in which each level is more specific than the one above it
What are kingdoms?
The broadest units of
classification are the kingdoms,
What are the kingdoms?
of which there are five: animal, plant, monera (bacteria),
protist (protozoa, algae, and some molds), and fungi (molds, mushrooms, yeasts, and the
like)
What are the classifications used to identify an organism?
The next six classifications become increasingly specific: phylum, class, order, family,
genus, and species.
What is active transport?
Active transport involves the use of energy in the form of ATP to move
substances across the membrane
What is passive transport?
Passive transport does not require energy and makes use
of diffusion and filtration.
What is diffusion?
In diffusion, particles move in a random manner, spreading evenly
throughout an available space and moving from regions of high concentration to those of low
concentration
What is osmosis?
A specific type of diffusion is that of water, or osmosis. Water moves from an area of high water concentration (or low particle concentration) to an area of low water concentration (high particle concentration)
What is isotonic?
When the solute concentration of the water is
the same as that inside the cell, the solution is said to be isotonic. Thus, the amount of water
that leaves the cell and the amount that enters it are equal.
What is hypertonic?
When the solute is more
concentrated outside the cell than inside it, the solution is hypertonic. As a result, the cell shrinks.
What is hypotonic?
If the solute concentration outside, the cell
is lower than that inside the cell, the solution is hypotonic. Water flows into the cell (again
high-water/ low-particle concentration to low-water/high-particle concentration). If the flow
continues long enough, the cell bursts
What is filtration?
Filtration is the movement of water and solutes through the membrane by fluid, or hydrostatic,
pressure.
What are autotrophs?
Autotrophs are organisms that produce their own food from inorganic substances (i.e. plants)
What are heterotrophs?
Heterotrophs, or consumers, on the other hand, obtain their food by consuming plants or
other animals.
What are secondary consumers?
Secondary consumers are carnivores (meat eaters) or omnivores that eat
herbivores.
What are herbivores?
Plant eaters
What are omnivores?
Plant and meat eaters
What are carnivores?
meat eaters
What are tertiary consumers
Tertiary consumers are carnivores that eat other carnivores or omnivores.
What are primary consumers?
Herbivores, omnivores.
What are the trophic levels of an ecosystem?
These divisions, which are made on the basis of how the organism meets its nutritional needs,
make up the trophic levels of an ecosystem.
What are the producers?
The autotrophs are the most important trophic
level in the ecosystem and are known as producers;
What is a food chain/food web?
The path along which food is transferred from level to level is called a food chain, and the interrelationship of many food chains is called a food web.
What are the functions of the decomposers/what are they?
An important role in an ecosystem is played by the decomposers, such as bacteria and fungi,
which consume nonliving organic material and release inorganic material.
What are factors that affect an ecosystem called?
Factors that affect an ecosystem are classified as biotic or abiotic.
what are biotic factors?
Biotic factors include the
living parts of the ecosystem,
What are abiotic factors?
and abiotic factors are nonliving influences, such as
temperature, humidity, or soil composition.
What is parasitism
parasitism (in which one species benefits and the other species is harmed, such as a tapeworm in a human host)
What is commensalism
commensalism (in which one species benefits
and one is unaffected, such as a remora and shark
What is mutualism
mutualism (in which both species
benefit, such as lichen, which is made up of a fungus and an alga and is found on a tree or
rock)
What is a biosphere?
a biosphere is the entire portion of our planet that is inhabited by living
things in a variety of ecosystems and communities
What are biomes?
Within the biosphere are groups of
ecosystems that are common to the various types of geographical areas. These geographical
areas are called biomes
What are tundras?
Tundras are characterized by very cold temperatures and high altitude. The conditions
allow shrubs and bushes to grow, but no trees.
What are deserts?
Deserts have little precipitation and are more arid than all of the other biomes.
What are tropical rain forests?
Tropical rain forests typically have a relatively constant temperature (68°F-90°F),
constant daylight length throughout the year, high humidity, and abundant rain (200-
400 cm/year). These forests are known for their biodiversity, having more species than
any other area of the world. Trees grow very tall and there is great competition for light.
Little light reaches the forest floor.
What are deciduous forests?
Deciduous forests are usually found in the temperate, mid-latitude regions of the
world, where the air contains enough moisture to support the growth of large trees.
Deciduous trees, such as oaks and maples, drop their leaves during the dry months.
The temperatures in this biome can range widely from season to season.
What are Coniferous forests
Coniferous forests (taigas) are found at high and cool elevations, where the seasons consist of short summers and long, chilly winters. These areas are characterized by conifers, such as pine, and firs, which do not shed their leaves in the cold, dry months.
What is photosynthesis?
To produce their own organic molecules from inorganic molecules in the environment,
autotrophs use the process called photosynthesis.
What does chlorophyll do?
In this process, the pigment chlorophyll,
which is located in the chloroplasts of plant cells, absorbs light energy. This energy, in turn,
drives the synthesis of food molecules
What is a cuticle plants?
The stems and leaves of most plants are covered by a cuticle, which is a waxy layer that helps
prevent water loss through evaporation.
What are stomates?
Additionally, the leaves have stomates, which are
pores on the lower surface of the leaves that allow carbon dioxide to enter and oxygen to be
released during photosynthesis without losing too much water.
What are angiosperms?
The flower in flowering plants,
or angiosperms, is responsible for reproduction
What are the sepals?
The sepals encase the flower
before it blooms.
What are the petals?
the petals are useful in attracting pollinators. In the center of the petals
are the stamen and pistils
What are the stamen?
The stamen consists of the filament, which supports the anther, where pollen is produced.
What does the pistil consist of?
The pistil consists of the stigma (which receives pollen), the style (which leads to the ovary), and the ovary (which contains the ovules and where fertilization
occurs).
How is fruit made?
After fertilization, the ovules within the ovary develop into seeds. The walls of the
ovary thicken to protect the seed and this thick fleshy protective layer is what we know and
love as fruit.
What are genes?
All living things possess a set of instructions (genes) that determines the characteristics of an
organism.
Where are genes?
On chromosomes
What is the law of dominance?
In observing pea plants, Mendel observed that, when individuals with contrasting traits are
crossed, one trait, called the dominant trait, is expressed, and the other trait, called the
recessive trait, is masked. This is the law of dominance
What does phenotype mean?
The phenotype, or appearance of the plants
What does homozygous mean?
An individual with two identical genes for a
trait is called purebred, or homozygous
What does heterozygous mean?
For example, if a tall plant (TT) is crossed with a short plant (tt), the result is 100%
heterozygous (Tt) offspring, containing one allele for tall and one for short
What is the law of segregation?
The law of segregation tells us that when two of these hybrids (heterozygotes) are crossed,
the hidden trait becomes segregated and appears in 25% of the offspring.
What is the law of independent assortment?
The law of independent assortment tells us that genes on different chromosomes are inherited independently of each other.
How many chromosomes do humans have?
46
What are autosomes?
Non sex chromosomes
What are sex linked traits?
For some traits, the genes are found only on the X chromosome, but not on the Y, and these traits are called sex-linked traits.
What is a nucleotide made of?
Each nucleotide is composed of a phosphate group (PO4), a five-carbon sugar called deoxyribose, and a nitrogenous base.
What is the double helix?
The nucleotides form long chains, which are joined to form a double helix.
What does guanine always pair with?
cytosine (C)
what does adenine always pair with?
Thyamine
What happens during replication of DNA ?
During replication, the DNA strand opens at the base pairs. Free (or unattached) nucleotides are incorporated into the unzipped portion of the DNA, so that
complementary base pairs join to form two exact duplicates
What is transcription?
The process of forming m-RNA according to the information contained in the DNA molecule is called transcription
How does transcription differ from translation?
RNA differs
from DNA in that it is single stranded, has the sugar ribose in place of deoxyribose, and
replaces thymine with uracil.
What is a light microscope?
In a light microscope, light is
first passed through a specimen and then through a glass lens, which bends light in such a
manner that an image is magnified
What is an electron microscope?
The electron microscope, which sends a
beam of electrons through a specimen, can be used to examine structures too small to be
seen through a light microscope.
How much can a light microscope magnify?
The light microscope can magnify specimens up to 2,000
times,
How much can a electron microscope magnify?
whereas the electron microscope can magnify them up to 2 million times
How much can the compound microscope magnify?
The compound microscopes you may have used in school usually magnify around 400 times,
under high power
What are variables?
During an experiment, we are often looking for data
on variables, which are measurable factors or qualities that change during an experiment.
What is an independent variable?
An independent variable is one that is changed by the experimenter.
What is the dependent variable?
The variable that changes in response to the independent variable is called the dependent variable
Where is the independent and dependent variable plotted on a graph?
When we represent data in the form of a graph, the independent variable is
always plotted on the x-axis and the dependent variable on the y-axis.
What is mechanical digestion?
breaking food into smaller pieces
What is chemical digestion?
chemical digestion (breaking nutrients into small molecules)
What is hydrolysis?
The process by
which chemical digestion occurs is called hydrolysis (splitting molecules by adding water).
What are the functions of enzymes in digestion?
Chemical digestion is sped up by the action of digestive enzymes (hydrolases
What is the alimentary canal?
Humans, as opposed to simpler animals, such as jellyfish, have a digestive system that is composed of a
tube that extends between two openings: the mouth and the anus. This tube,
called the alimentary canal
What are the accessory glands of the digestive system?
(liver, gallbladder, and pancreas).
What is the surface area (digestive system)
Food enters through the mouth, where it is chewed (mechanical digestion), increasing the
surface area, which makes it easier to both swallow and digest.
What do the salivary glands do?
The presence of food also
stimulates the salivary glands to release saliva, which contains an enzyme called amylase.
What does amylase do?
Amylase breaks down starches into smaller carbohydrate molecules (monosaccharides and
disaccharides)
What is the function of the epiglottis?
While swallowing, the top of the
windpipe is covered by the epiglottis to prevent food from entering the respiratory system.
What is peristalsis?
From the esophagus, the food is passed to the stomach by muscular contractions called
peristalsis.
What does the lining of the stomach do for digestion?
The lining of the stomach releases gastric juice, which is made up of hydrochloric acid and
proteases (protein digesting enzymes)
What is chyme?
The smooth muscles of the stomach mix the partially digested food and the result is a liquid called chyme
What does the pyloric sphincter do?
Chyme is released to the small intestine in a series of small portions through the pyloric sphincter.
Where does most of the digestion take place in humans?
Most of the digestion of food takes place in the small
intestine, which can be up to 6 meters long in humans. The small intestine is the major site not only for digestion but also for the absorption of
nutrients into the bloodstream. Digestive enzymes are secreted by intestinal glands.
What does the liver do in terms of digestion?
The liver produces bile, a substance stored and concentrated in the gallbladder, which helps in the
breakdown of fats.
What does the pancreas do in terms of digestion?
The pancreas supplies a number of enzymes needed for digestion.
what do the villi do?
To facilitate absorption, the small intestine is lined with villi, which greatly increase the intestinal
surface area for the absorption of the end products of digestion into the blood and lymph.
What happens to the undigested food?
Undigested food is moved to the large intestine, or colon, which is responsible for
reabsorbing water that has entered the alimentary canal.
Where is the waste stored?
Waste, or feces, moves along the colon by peristalsis, becoming increasingly solidified and is ultimately stored in the rectum until egestion (elimination from the body).
How does diarrhea and constipation occur?
. Diarrhea is a result of peristalsis moving feces
through the colon too quickly so that water is not reabsorbed, whereas constipation results
from too little peristalsis and thus too much reabsorption of water
What is circulation?
Circulation is the internal transport of blood and lymph throughout the body, which allows for
the exchange of gases, the absorption of nutrients, and the disposal of waste.
What is the circulatory system made up of?
The circulatory system is made up of the cardiovascular and lymphatic system, which function together to
achieve these goals.
What is the cardiovascular system made up of?
The cardiovascular system in humans is made up of the heart, blood vessels, and blood.
What are the four chambers of the heart?
Two atria, two ventricles.
What do the atria do?
: two atria (singular: atrium), which receive blood
What do the ventricles do?
ventricles, which pump blood to the body
Where does the blood from the body enter the heart?
Blood enters the right atrium from the upper and lower body through veins called the
superior vena cava and the inferior vena cava.
What is the atrioventricular valves functions?
From there, it passes through an atrioventricular valve into the right ventricle (valves
prevent backflow when ventricles contract).
What do the pulmonary arteries do?
The right ventricle pumps blood through the semilunar valve into the pulmonary arteries,
which carry the blood to the lungs. This blood is deoxygenated and becomes oxygenated
in the lungs where gas exchange occurs.
What do the pulmonary veins do?
Newly oxygenated blood leaves the lungs via the pulmonary veins, which returns blood to
the left atrium.
What does the left ventricle do?
From there, it passes through another atrioventricular valve to the left ventricle.
Muscular contractions of the left ventricle pump blood through the aorta to all parts of the
body.
What is systole?
When the heart
contracts, the pressure increases (systole),
What is diastole?
When the heart relaxes, the pressure decreases diastole
What are the three ways blood circulates?
There are three ways blood circulates: coronary circulation, (circulation of
blood to the heart ), pulmonary circulation (circulation of blood through the lungs), and
systemic circulation (circulation throughout the body).
What is blood?
Interestingly, blood is considered a type of connective tissue that is made up of variety of cells
suspended in a liquid called plasma.
What is the composition of blood?
Red blood cells, white blood cells, and
platelets make up 45% of whole blood, whereas plasma, which contains proteins, ions,
hormones, and gases, makes up the other 55%
What do red blood cells do?
Red blood cells, or erythrocytes, are
responsible for transporting oxygen, and they do not have nuclei or mitochondria.
How many molecules of hemoglobin per red blood cell?
To suit their
main function of transporting oxygen, red blood cells are small and thin (to allow for diffusion),
and each cell contains approximately 250 million molecules of hemoglobin, an oxygen carrier.
Why is iron necessary in our diets?
Hemoglobin is an iron-rich globular protein, which explains the need for iron in our diets.
What do white blood cells do?
White blood cells, or leukocytes, are less abundant than red blood cells and are involved in
host defense. Not surprisingly, an infection is indicated when the number of white blood cells
exceeds the normal concentration.
What do platelets do?
Platelets, also found in plasma, are pieces of cells that are important in blood clotting.
What do lymph capillaries do?
As blood passes through the capillary vessels of the circulatory system, fluid and proteins can
leak out into the interstitial space. This lost fluid diffuses into lymph capillaries, which are
found throughout the cardiovascular system, and thus enters the lymphatic system. Inside the lymphatic system, the fluid, or lymph, returns to the circulatory system
What do lymph nodes do?
Lymph nodes are special pockets in the lymphatic system where the lymph is filtered. White
blood cells are present in these nodes to attack bacteria and viruses that may be present in
the fluid. This is why swollen and tender lymph nodes are usually a sign of an infection.
What are the three kinds of blood vessels?
There are three kinds of blood vessels: arteries, veins, and capillaries
What are the functions of arteries?
Arteries transport blood away from the heart. Because they carry blood at relatively high pressure, they are muscular. We feel a pulse in the arteries
What are the functions of veins?
Veins transport blood to the heart, and they contain valves to prevent the backflow of blood as it returns to the heart.
What are the functions of capillaries?
Capillaries are tiny blood vessels that
connect arteries and veins. It is through the capillary walls (only one cell thick) that nutrients
and oxygen leave the blood to enter the interstitial space and tissue cells and waste products
and carbon dioxide leave the tissue to enter the blood.
What is the order of taking a breath?
Air enters the respiratory system through the nasal cavities, which lead to the pharynx, then to the larynx, then the air travels to the trachea, or windpipe, which branches into two main bronchi, which lead to the lungs. Inside each lung, the branching continues, creating thinner and thinner tubes called bronchioles, and at the end of these bronchioles are alveolus.
What is an alveolus?
An air sac. These thin and permeable air sacs are the functional units of the lung.
what does the diaphragm do in terms of respiration?
This involves the muscular movement of the diaphragm (a sheet of muscle lining the bottom of the
thoracic cavity) and of the rib cage, which raises and lowers the pressure in the chest cavity.
What is cellular respiration?
Cellular respiration is the process by which we get energy from the food that we eat.
What is aerobic respiration?
Aerobic respiration occurs when oxygen is present,
and it is the opposite process to that of photosynthesis
What is anaerobic respiration?
If oxygen is not present, anaerobic respiration occurs, which is less efficient, producing a lower amount of
ATP.
What is the production of lactic acid a result of?
. Lactic acid, which is produced during anaerobic respiration, is a cause of sore muscles
after strenuous exercise.
What is anaerobic respiration called in yeast, and why
Anaerobic respiration in yeast is called fermentation, producing
ethanol rather than lactic acid.
What does the nervous system do?
The nervous system directly regulates body functions and responds to environmental stimuli.
What is the functional unit of the nervous system?
The functional unit of the nervous system is the neuron
Why do neurons at rest have an electrical potential?
At rest, neurons have an electrical potential due to differences in sodium and potassium ion concentrations across the cell membrane
What is an impulse?
Generally, an impulse is generated when the dendrites of a neuron are stimulated by the environment or by another neuron.
How does the impulse travel?
The impulse travels from the cell body along the axon until it reaches the ends (axon terminals)