biology chapter 2 Flashcards
cell division
is the process by which a cell doubles its organelles and cytoplasm, replicates its DNA, and then divides in two
unicellular organisms
cell division is a means of reproduction
multicellular organisms
is a method of growth, development, and replacement of worn-out cells
mitosis
is the division and distribution of the cell’s DNA to its two daughter cells such that each recieves a complete copy of the original genome
karyokinesis
nuclear division
cytokinesis
cell division
interphase
a period of growth and replication of genetic material prior to the initiation of mitosis
prophase
the chromosomes condense, and the centriole pairs separate and move towards the opposite poles of the cell. The spindle apparatus forms between them and the nuclear membrane dissolves, allowing the spindle fibers to interact with the chromosome
metaphase
the centriole pairs are now at opposite poles of the cell. The fiers of the spindle apparatus attach to each chromatid at the centromere to align the chromosomes at the center of the cell forming the metaphase plate
anaphase
the centromeres split so that each chromatid has its own distinct centromere, thus allowing sister chromatids to separate. The sister chromatids are pulled toward the opposite poles of the cell by the shortening of the spindle fibers.
telophase
the spindle apparatus disappears. A nuclear membrane forms around each set of newly formed chromosomes. Thus each nucleus contains the same number of chromosomes as the original or parent nucleus. The chromosomes uncoil, resuming their interphase form
cytokinesis
near the end of telophase, the cytoplasm divides into two daughter cells, each with a complete nucleus and its own set of organelles
cleavage furrow
in animal cells,. The cell membrane indents along the equator of the cell and finally inches through the cell, separating the two nuclei
plant cells
lack centrioles. The spindle apparatus is synthesized by microtubule organizing centers which are not visible. Are rigid and cannot form a cleavage furrow. They divide by the formation of a cell plate
cell plate
an expanding partition that grows outward from the interior of the cell until it reaches the cell membrane
meiosis
is the process by which these sex cells are produced. Produces the haploid (!N) number, halving the number of chromosomes. Involves two divisions of primary sex cells resulting in four haploid cells called gametes
interphase
the parent cell’s chromosomes are replicated during interphase resulting in the 2N number of sister chromatids
first meiotic division
the first division produces two intermediate daughter cells with N chromosomes with sister chromatids
prophase I
the chromatin condenses into chromosomes, the spindle apparatus forms, and the nucleoli and nuclear membrane disappear
synapsis
homologous chromosomes come toggether and intertwine
tetrad
each synaptic pair of homologous chromosomes contains four chromatids
crossing over
chromatids of homologous chromosomes break at corresponding points and exchange equivalent pieces of DNA
metaphase I
homologous pairs (tetrads) align at the equatorial plane, and each pair attaches to a separate spindle fiber by its kinetochore
anaphase I
the homologous pairs separate and are pulled to opposite poles of the cell
disjunction
each chromosome of paternal origin separates (or disjoins) from its homologue of maternal origin, and either chromosome can end up in either daughter cell
telophase I
a nuclear membrane forms around each new nucleus. At this point, each chromosome still consists of sister chromatids joined at the centromere
second meiotic division
the chromosomes aligh at the equator, separate and move to opposite poles, and are surrounded by a reformed nuclear membrane
asexual reproduction
is the production of offspring without fertilization
fission
binary fission is a simple form of asexual reproduction seen in prokaryotic organisms. The DNA replicates and a new plasma membrane and cell wall grow inward along the midline of the cell, dividing it into two equally sized cells with equal amounts of cytoplasm, each containing a duplicate of the parent chromosome
budding
is the replication of the nucleus followed by unequal cytokinesis. The cell membrane pinches inward to form a new cell that is smaller in size but genetically identical to the parent cell, and which subsequently grows to adult size. The new cell may separate immediately from the parent or it may remain attached to it, develop as an outgrowth, and seaparate at a later stage
regeneration
is the regrowth of a lost or injured body part. Replacement of cells occurs by mitosis
parthenogenesis
is the development of an unfertilized egg into an adult organism. This process occurs naturally in certain lower organisms
spore formation
all plants exhibit alternation of generations in which a diploid generation is succeeded by a haploid generation. The diploid sporphyte generation produces haploid spores which develop into the haploid gametophyte generation
vegetative propagation
undifferentiated tissues in plants, called meristems, provide a source of cells that can develop into an adult plant. Can occur naturally, or through human intervention. Is advantageous because it introduces no genetic variation and is a rapid form of reproduction
bulbs
split to form several bulbs.
tubers
are underground stems with buds, like the eyes of potatoes, that can develop into adult plants
runners
are stems running above and along the ground, extending from the main stem. Can produce new roots and upright stems as they do in strawberry and lawn grasses
rhizomes
are woody, underground stems. They can develop new upright stems as they do in ferms and iris plants
auxins
synthetic plant hormones that can be used to accelerate root formation
layering
stems of certain plants wil take root when bent to the ground and covered with soil
sexual reproduction
occurs via the fusion of two gametes- specialized sex cells produced by each parent. Requires: the production of functional sex cells or gametes by adult organisms, the union of these cells (fertilization or conjugation) to form a zygote, and the development of the zygote into another adult, completeing the cycle
gonads
specialized organs where the gametes are produced
testes
the male gonads that produce sperm in the tightly coiled seminiferous tubules
ovaries
the female gonads that produce oocytes (eggs)
hermaphrodites
which have both functional male and female gonads
spermatogenesis
sperm production. Occurs in the seminiferous tubules
mature sperm
is an elongated cell with a head, tail, neck, and body
head
consists almost entirely of the nucleus which contains the paternal genome
tail (flagellum)
propels the sperm, while mitochondria in the neck and body provide energy for locomotion
oogenesis
the production of female gametes, occurs in the ovaries
polar body
which is a small cell that contains little more than the nucleus
fertilization
is the union of the egg and sperm nuclei to form a zygote with a diploid number of chromosomes
external fertilization
occurs in vertebrates that reproduce in water. The female lays eggs in the water and the male deposits sperm in the vicinity. The lack of direct passage of sperm from male to female reduces the chances of fertilization considerably
internal fertilization
is practiced by terrestrial vertebrates and provides a direct route for sperm to reach the egg cell. This increases the chance for fertilization success and females produce fewer eggs.
testosterone
regulates secondary male sex characteristics including facial and pubic hair, and voice changes
spermatogonia
diploid cells that differeniate into diploid cells
spermatozoa
are specialized for transporting the sperm nucleus to the egg
acrosome
a cap like structure derived from the golgi apparatus, develops over the anterior half of the head. Contains enzymes needed to penetrate the tough outer covering of the ovum
ovaries
found in the abdominal cavity, below the digestive system
follicle
is a multi-layered sac of cells that contains, nourishes, and protects an immature ovum
uterus
site of fetal development
cervix
lower, narrow end of the uterus. Connects with the vaginal canal
vaginal canal
is the site of sperm deposition during intercourse and is also the passageway through which a aby is expelled during child birth
estrogens
are steroid hormones necessary for normal female maturation. They stimulate the development of the female reproductive tract and contribute to the development of secondary sexual characteristics and sex drive. Are also responsible for thickening of the endometrium (uterine wall). are secreted by the ovarian follicles and the corpus luteum
progesterone
is a steroid hormone secreted by the corpus luteum during the luteal phase of the menstrual cycle. Stimulates the development and maintenance of the endometrial walls in preparation for implantation
menstrual cycle
can be divided into the follicular phase, ovulation, the luteal phase, and menstruation
follicular phase
begins with the cessation of the menstrual flow from the previous cycle. FSH from the anterior pituitary promotes the development of the follicle, which grows and begins secreting estrogen
ovulation
a mature ovarian follicle bursts and releases an ovum midway through the cycle. Is caused by a surge in LH which is preceded, and in part caused, by a peak in estrogen levels
luteal phase
LH (luteinizing hormone) induces the ruptured follice to develop into the corpus luteum, which secretes estrogen and progesterone. Progesterone causes the glands of the endometrium to mature and produce secretions that prepare it for the implantation of an embryo
menstruation
the resulting drop in progesterone and estrogen levels caues the endometrium to slough off, giving rise to the menstrual flow
oogenesis
is the production of female gametes, occurs in the ovarian follicles
primary oocytes
all of the immature ova that a female will produce during her lifetime are already in her ovaries. They are diploid cells that form by mitosis in the ovary
fertilization
an egg can be fertilized during the 12-24 hours following ovulation. Occurs in the lateral, widest portion of the fallopian tube.
monozygotic (identical) twins
result when a single zygote splits into two embryos. Are genetically identical, since they develop from the same zygote. They are therefore of the same sex, blood type, and so on.
dizygotic (fraternal) twins
result when tw ova are released in one ovarian cycle and are fertilized by two different sperm. They share no more characteristics than any other siblings since they develop from two distinct zygotes
haploid gametophyte generation
produces gametes by mitosis. Union of the male and female gametes at fertilization restores the diploid sporophyte generation
diploid sporophyte generation
produces a haploid (monoploid) spore by meiosis. The spores divide by mitosis to produce the haploid or gametophyte generation
flower
is the reproductive structure of angiosperms
stamen
is the male organ of the flower and consits of a thin stalk like filament with a terminal sac called the anther. The anther produces monoploid spores which develop into pollen grains
epicotyl
this is the precursor of the upper stem and leaves
cotyledons
these are the seed leaves. Dicots have two seed leaves while monocots have only one
hypocotyl
this develops into the lower stem and root
endosperm
the endosperm grows and feeds the embryo. In dicots, the cotyledon absorbs the endosperm
seed coat
develops from the outer covering of the ovule. The embryo and its seed coat together comprise the seed
apical meristem
is found in the tips of roots and stems. Growth in length occurs only at these points
lateral meristem
or cambium is located between the xylem and phloem. This tissue permits growth in diameter and can differentiate into new xylem and phloem cells
