Extras Es Flashcards
Ectotherm
An animal such as a reptile whose
temperature fluctuates with that of its
environment. Many ectotherms, however, are
able to keep their internal temperature within a
narrow range by moving from one part of their
environment to another. A marine iguana, for
example, moves between water and land with
the result that its internal temperature varies very
little
Egg cell, Egg nucleus
A haploid sex cell or
gamete, produced by meiosis in female sex
organs. Egg cells are found inside the embryo
sac in the ovary of a flowering plant, and in the
ovaries of a woman. An animal egg cell is also
known as an ovum. The egg cell fuses with a male gamete to form a zygote. The zygote
grows and divides by mitosis to form an
embryo.
Endoplasmic reticulum
System of flattened,
membrane-bound sacs found in the cytoplasm.
It plays a role in the synthesis and transport of
molecules within the cell.
Embryo
When a female gamete is fertilised, a
zygote is formed. In animals and plants this
zygote grows and divides by mitosis, eventually
becoming a new adult. The term embryo is used
to describe the early stages in development. The
embryo of a flowering plant is found inside a
seed. A mammalian embryo develops inside the
uterus of its mother.
Endotherm
An animal such as a mammal whose
temperature changes very little whatever the
temperature of its surroundings. Endotherms rely
on physiological processes such as sweating and
shivering to maintain their temperature.
Environment, Environmental
The conditions of
the external environment which affect an
organism can be divided into two groups.
Abiotic factors are concerned with the nonliving
part of the environment; temperature and
rainfall are abiotic factors. Biotic factors involve
other organisms; competition is a biotic factor.
Equator
At cell division, the widest part of the
cell, mid-way between the poles.
Erector muscle
A muscle in the dermis of the
skin. Contraction of the erector muscles causes
the hairs to stand upright and trap a layer of air
next to the skin. The trapped air acts as an
insulator and helps in thermoregulation.
Essential amino acid
An amino acid that the
body needs but is unable to make itself.
Essential amino acids have to be present in the
diet in amounts sufficient to meet the needs of
the body.
Eugenics
Use of selective inheritance to attempt
to improve the human race.
Eutrophication
An increase in the quantity of
plant nutrients such as nitrogen and phosphorus,
particularly in aquatic ecosystems. Large
amounts of nitrate and phosphate resulting from
pollution by excess fertiliser or sewage causes
an increase in algae and other photosynthetic
organisms. These die and the increased
respiration of decomposers results in a lower
oxygen concentration and the death of many
aquatic animals.
Excretion
The removal of waste products that
have been produced in reactions which take
place in the body. Urea and other substances are
excreted by the kidney. The lungs are also
excretory organs, removing carbon dioxide
formed as a product of respiration from the
body. Many drugs are eventually broken down
in the body and the products are excreted by the
kidneys.
Exocrine
A gland that secretes substances into a
duct is called an exocrine gland. The salivary
glands and the pancreas are examples of
exocrine glands.
Extinction
The process by which a species
becomes extinct. A species is extinct when there
are no living members of the species in the wild
or in captivity.
