E–H
E
- ear
- Sensory
organ capable of detecting sound.
- ecological succession
-
The progression of plant life and attendant animal life
in a given geographic location, from pioneer plant to climax community.
- ecology
- The
study of the interactions and relationships of populations with
each other and their abiotic environments.
- ecosystem
- A
community of organisms and its abiotic environment.
- ectotherm
- See
cold-blooded.
- egg
- The female
gamete in sexual reproduction; also called an ovum.
- electron microscope
-
An instrument that uses an electron beam to form clear
and highly magnified images of microscopic structures. Electron
microscopes cannot take pictures of living organisms.
- electron transport chain
-
The final stage of aerobic respiration. The electron
transport chain establishes an electrochemical gradient across the
inner mitochondrial membrane that powers the synthesis of ATP in
oxidative phosphorylation.
- embryo
- Before
birth, the maturing cells that will grow into a fully formed organism.
- endocrine system
- Control
system of the body that functions by releasing hormones into the bloodstream.
- endocytosis
- Process
by which liquids or small solid particles are taken into a cell
in the form of small vesicles that are produced through the invagination
of the cell membrane.
- endoplasmic reticulum
-
A network of membrane-bound tubes and sacs in the cytoplasm.
The endoplasmic reticulum is a major site of protein and lipid synthesis.
- endoskeleton
- An
interior skeleton found in vertebrates made of bone and cartilage.
- endotherm
- See
warm-blooded.
- energy pyramid
- Energy
in a community can be depicted as a pyramid of food or biomass.
The availability of food, biomass, and energy from the trophic level
of producers up through each subsequent level on the food web is
approximately 10 percent of that available in the previous trophic
level.
- enzymes
- Biological
catalysts made from proteins. Enzymes have attachment locations
for substrates called active sites.
- estrogen
- Hormone
that stimulates the growth of the uterine lining during pregnancy
and that develops and maintains the female secondary sex characteristics,
such as the development of mammary glands, a narrower waist and
wider hips, axillary and pubic hair, and a higher-pitched voice.
- eukaryote
- An
organism whose cells have membrane-bound intracellular organelles,
including a nucleus containing multiple chromosomes. Eukaryotes,
unlike prokaryotes, can undergo sexual reproduction via meiosis.
Compared to prokaryotes, eukaryotes are more complex and arose later
in evolutionary history. Protists, fungi, plants, and animals are
all eukaryotic organisms.
- excretory system
- The
organ system that filters blood and removes nitrogenous wastes from
the body in the form of urea or uric acid. In humans, the two kidneys
are the vital organs of blood filtration. In annelids, nephridia
fill the filtering role; Malpighian tubules do the same in arthropods.
In humans, other important structures of the system are the ureters,
the urinary bladder, and the urethra.
- exocytosis
- Process
by which molecules are secreted from the cell. Exocytosis occurs
when a vesicle fuses with the cell membrane and releases its contents
to the outside.
- exoskeleton
- A
rigid, chitinous protective structure that surrounds the bodies
of arthropods and provides support.
- eye
- Sensory
organ capable of detecting light.
F
- F1 generation
-
The first generation of offspring from a cross between
two varieties or individuals. In Mendel’s experiments, all the F1 offspring
were heterozygous hybrids with a dominant phenotype.
- F2 generation
-
The second generation of offspring in a breeding experiment;
the offspring from a mating between two F1 hybrids.
In Mendel’s monohybrid experiments, the ratio of dominant to recessive
phenotypes in the F2 generation
was 3:1.
- facilitated diffusion
-
Diffusion of molecules that cannot pass through the
cell membrane independently, but rather through permeable protein
channels embedded in the membrane. Facilitated diffusion does not
require outside energy.
- FADH2
-
A molecule that stores energy for harvest by the electron
transport chain.
- Fallopian tube
- Duct
that connects the ovaries with the uterus; the passage through which
the ovulated egg travels from the ovaries to the uterus.
- fermentation
- The
second stage of anaerobic respiration, which produces the NAD+ necessary for
glycolysis. There are two types of fermentation: alcoholic fermentation
and lactic acid fermentation. Yeast engage in alcoholic fermentation,
while muscle cells lacking oxygen produce lactic acid.
- fetus
- The name
given to an embryo after it has developed organs.
- flagellum
- A
whiplike structure projecting from the surface of some cells and
single-celled organisms; coordinated waving of the flagellum allows
the organism to swim. Prokaryotic flagella are made of a single
helical chain of flagellin proteins; eukaryotic flagella are made
of multiple chains of microtubule proteins.
- fluid-mosaic model
-
Theory describing the cell membrane as a dynamic structure
with proteins floating, yet partially embedded, in a sea of phospholipids.
- food chain
- A
linear relationship of predators and prey.
- food web
- Many
connected food chains that exhibit the relationships of all predators
to all prey constitute a food web.
- fossil record
- The
grouping of fossilized remains according to relative and absolute
age.
G
- gallbladder
- An
organ that stores the bile produced by the liver and releases it
to the small intestine during digestion.
- gamete
- A haploid
sex cell (either an egg or sperm cell); male and female gametes
join during fertilization to create a diploid zygote. Gametes are
created out of germ cells and are passed down to offspring.
- gametophyte
- A
haploid plant or plant structure that produces haploid gametes through
mitosis.
- ganglion
- A
simple cluster of nerve cells that acts as a coordinating center.
In more sophisticated organisms, ganglia evolved into a brain and
spinal cord.
- gene
- The fundamental
unit of heredity, composed of a stretch of DNA. In general, a single
gene encodes the information needed to produce one kind of protein.
Each gene resides in a specific spot on a chromosome.
- gene flow
- The
movement of genes, within a population or between populations, through mating.
- genetic code
- The
series of codons that make up an organism’s DNA.
- genotype
- The
entire set of specific alleles present in an organism or cell: the
genetic information that (together with the environment) defines
the phenotype. Often refers only to the alleles controlling a particular
trait of interest.
- germ cell
- Cells
that lead to the production of gametes. Produced by meiosis.
- glucose
- A monosaccharide
with the chemical formula C6H12O6.
Used as the raw material for cellular respiration.
- glycolysis
- The
first step of aerobic and anaerobic respiration. Glycolysis produces ATP while converting
glucose to pyruvate, which is the raw material for the rest of aerobic
respiration.
- Golgi apparatus
- A
series of membrane-bound sacs in the eukaryotic cytoplasm. The Golgi apparatus
takes proteins produced by the endoplasmic reticulum and packages
and secretes them to various destinations inside and outside of
the cell.
- gonads
- Sex
organs that produce gametes. The gonads also release sex hormones,
such as testosterone, estrogen, and progesterone. In humans, the
male gonads are the testes; in females, the ovaries.
- grafting
- An
artificial form of vegetative propagation in which parts of two
young plants are joined together, first by artificial means and
then by tissue regeneration.
- Gram staining
- A
process by which components of bacterial cell walls are bound to
Gram’s stain. Depending on the amount of peptidoglycan in their
cell walls, bacteria stain differently and are classified as Gram-negative
or Gram-positive.
- guard cells
- Epidermal
plant cells found in pairs surrounding the stomata of leaves. By increasing
or decreasing their size, guard cells regulate gas exchange by opening
and closing individual stoma.
- gymnosperm
- A
vascular nonflowering plant (commonly known as a conifer) in which
seeds are “naked”—collected in a cone and not protected by an ovary.
The dispersion of their spermatozoids often relies on wind.
H
- haploid number
- The
number of homologous pairs in a cell. Equal to half the diploid
number. Gametes, cells that are passed on to offspring, contain
the haploid number of chromosomes. In humans, the haploid number
is 23.
- heart
- The muscular
organ that pumps blood through the circulatory system. Mammals and birds
have a four-chambered heart, with a left atrium and ventricle and
a right atrium and ventricle. The right half of the heart receives
deoxygenated blood from the body and pumps it to the lungs, while
the left half receives oxygenated blood from the lungs and pumps
it to the body.
- heredity
- The
genetic transmission of traits from parents to offspring, so that
offspring resemble their parents. Traits transmitted this way are
called hereditary traits.
- heterotrophs
- Organisms
that can only get the organic molecules and energy necessary for
life through the consumption of other organic matter. In the food
web, all consumers and decomposers are heterotrophs. Heterotrophs
can be herbivores, carnivores, or omnivores.
- heterozygous
- A
situation in which an individual (heterozygote) possesses two dissimilar
alleles for the same gene. The opposite is homozygous.
- homologous chromosomes
-
Chromosomes containing the same series of genes; they
may or may not carry the same alleles. Humans receive one set of
23 paternal chromosomes from their male parent and another set of
23 maternal chromosomes from their female parent. Each set matches
up to the other for a total of 23 different pairs of homologous
chromosomes. During meiosis, homologous pairs line up and are separated.
In males, the X and Y chromosomes act as a homologous pair, although
they are only partially homologous.
- homologous trait
- A
trait found in different species that are morphologically and functionally similar
and that comes from the same ancestral condition. A whale’s fin
and a human’s arm are homologous structures.
- homozygous
- A
situation in which an individual (homozygote) has the exact same
allele on both homologous chromosomes. Mating of two individuals
with the same homozygous genotype will produce only offspring with
that same identical genotype. The two identical alleles may be dominant
or recessive (e.g., RR or rr). The opposite of homozygous is heterozygous.
- hormones
- A
chemical messenger that can be made of either peptides or lipids.
Secreted by glands in one part of the body, hormones affect glands
or organs in another part.
- hybrid
- A genetic
mixture; the offspring of two genetically different parents. Hybrids
are usually heterozygous for a variety of genes.
- hydrogen bond
- A
weak bond between hydrogen and a set of other elements, including
oxygen. Hydrogen bonds are a subset of dipole-dipole interactions.
- hydrolysis
- A
common biochemical reaction in which the bond between two molecules
is split by the addition of a water molecule. Hydrolysis is the
process that breaks down polymers and dimers. The reverse is dehydration
synthesis.
- hydrophilic
- Having
an affinity for water; usually polar molecules. For the SAT II Biology,
this is principally important in relation to the phospholipid bilayer.
- hydrophobic
- Having
a reluctance to mix with water; usually nonpolar molecules. The
fatty acids that form the interior pocket between the two layers
of the cell membrane are hydrophobic.
- hydrostatic skeleton
-
A fluid skeleton in many soft-bodied invertebrates,
including annelids, that allows an organism to change shape but
not volume.
- hypertonic
- A
situation in which the concentration of solutes in a solution is
higher than what it contains. For example, a sodium solution of
10 percent would be hypertonic to an animal cell (with a sodium
concentration of about 0.9 percent), causing water to leave the
cell by osmosis.
- hypothalamus
- Part
of the brain responsible for temperature regulation, controlling
hunger and thirst, and managing water balance. It also helps generate
emotion.
- hypotonic
- A
situation in which the concentration of solutes in a solution is
lower than what an organism contains. An example is a paramecium
in pond water: the organism has more solutes than its environment,
so water flows into the cell by osmosis. Paramecia have evolved
contractile vacuoles to keep from exploding.
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