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366 terms

bio final

STUDY
PLAY
stamen
male structure
anther
holds pollen (fuzzy)
filament
holds anther
petal
attracts pollenators
sepal
protects bud
carpel/pistil
female structures
stigma
catches pollen
style
holds stigma and ovary together
ovary
holds the egg
double fertilization
A mechanism of fertilization in angiosperms, in which two sperm cells unite with two cells in the embryo sac to form the zygote and endosperm.
seed coat
tough outer coat-protects embryo and sperm
cotyledon
stores and transfers nutrients to embryon
monocots: 1 cotyledon
dicots: 2 cotyledons
fruit
protects seend once dormant
seed dispersal
burr: sticks to animals
fruit: eaten by animals that passes through digestive tract
water: water currents
wind
seed germination
the plant embryo begins to grow (favorable conditions)
hooked shoots: dicots
middle of shoot pushes up first
protects shoot as it comes through soil
(2 cotyledons)
sheath: monocots
another tube that creates a path for the plant to grow
(1 cotyledon)
seedling
the first moment the plant is above ground
environmental conditions
cacti live in dry, desertous areas and there isn't much rainfall-so they have to store H2O in their roots
other adaptations
long periods of cold: won't germinate in winter
brush fire: less competiotion for resources
natural selection: survive in extreme environments with adaptations
vegetative reproduction
a sexual reproduction in plants/with human help
fibrous roots
monocots: roots are spread out which will increase exposure to soil (minerals/nutrients) and water
taproots
dicots: one large central root with smaller brances
(like carrots)
nodes
points where leaves are attached to the stem
internodes
portions of stem between nodes
stem tissue
runs vertically in the stem to transport nutrients and minerals from the roots to the leaves
food is also transported down from the leaves to the shoots
terminal buds
buds on the top of the stem
axillary
buds off the sides of the stem
annuals
complete life cycle (germinate, grow, produce flowers and seeds, and die) in a single growing season
biennials
2 years and usually only flowers in 2nd year
perennials
live/reproduce in multiple years
dermal tissue
"skin" of the plant
(epidermis-protects young plants)
(cuticle)
vascular tissue
structural support
transports H20, minerals, nutrients, organic molecules between roots and shoots
(xylem: transports H20 up to leaves)
(phloem: transports food to roots-down)
ground tissue
storage and support
makes up most of a young plant and function in photosynthesis
(root cortex)
parenchyma cells
abundant cells-fruits
thin cell walls with large central vacuoles
(function: food storage, photosynthesis and respiration)
collenchyma cells
-young stems/petioles have this below the surface
-unevenly thick cells walls & grouped in strands/cylinders
-(f: provide support for growing plants
provide some flexibility)
sclerenchyma cells
-supports the plant, thick cell walls,lignin-rich cell walls
-grow and die within a mature part of a plant; leave their lignin-rich cells behind creating a "skeleton"
-(f: "skeleton" that supports plant, specialized for support
meristems
tissue that generate new dermal, vascular, and ground tissue in plants throughout their lives
apical meristem
meristem in the tips of roots and shoots
root cap
the very tip of the root (protects the cells of the apical meristem)
apical meristem functions
1) replaces the cells of the root cap that are scraped away by the soil
2) produces cells for primary growth
adaptation
inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment
HMS Beagle
ship Darwin sailed on
Galapagos Islands
where Darwin first developed his evolution ideas
Charles Lyell
gradual and observable geologic processes such as erosion could explain the physical features of nature-Earth was older than previously thought
Thomas Malthus
struggle for exsistence
population is growing too fast for food production
descent with modification
descendants of the earliest organisms spread into various habitats over millions of years-in these habitats they accumulated different adaptations to the diverse ways of life
natural selection
process by which induviduals with inherited characteristics well-suited to the environment leave more offspring on average than other induviduals (result is adaptation)
fossils
preserved remains or marking left by organisms that lived in the past
fossil record
chronological collection of life's remains in the rock layers, recorded during the passage of time
extinct
species that no longer exsist
homologous structures
Structures in different species that are similar because of common ancestry
vestigial structures
remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species
population
a group of induviduals of the same species living in the same area at the same time
variation
refers to differences among members of the same species
artificial selection
selective breeding of domesticated plants/animals to produce offspring with genetic traits that humans value
gene pool
consists of all the alleles (alternative forms of genes) in all the induviduals that make up a population
frequency of alleles
how often certain alleles occur in the gene pool
microevolution
evolution on the smallest scale-generation to generation change in the frequency of alleles within a population
Hardy-Weinberg Equilibrium
populations that don't undergo change to their gene pools are not presently evolving
genetic drift
a change in the gene pool of a population due to chance
Bottleneck Effect
reducing the size of a gene pool due to chance (natural disasters)
Founder Effect
when a few induviduals colonize on an isolated island, lake, or somewhere else new to habitat-the smaller the colony, the less genetic makeup there is to represent the gene pool of the larger population (chance reduces genetic variation)
gene flow
the exchange of genes with another population
mutation
a change in an organism's DNA
fitness
the contribution that an induvidual makes to the gene pool of the next generation compared to the contributions of other induviduals-HAS to be able to reproduce
biological species concept
defines a species as a population or group of populations whose members have the ability to breed with one another in nature and produce fertile offspring
macroevolution
encompasses more dramatic biological changes-origin of new species, extinction of species, and the evolution of major new features of living things-over a LONG period of time
speciation
the origin of new species
reproductive isolation
some kind of barrier that keeps 2 species from interbreeding
timing
different breeding seasons
behavior
two similar species may have different courtships or mating behaviors (dances, sounds etc.)
habitat
one lives on land, the other in water...no babies for them
physically incapable
an elephant and a mouse just can't do it...
geographic isolation
seperation of populations as a result of geographic change or dispersal to geographically isolated places
adaptive radiation
such evolution from a common ancestor that results in diverse species adapted to different environments
punctuated euilibrium
species often diverge in spurts of relatively rapid change
embryology
the study of the processes of multicellular organisms as they develop from fertilized eggs to fully formed organisms
geological time scale
organizes Earth's history into 4 distinct ages known as the Precambrian, Paleozoic, Mesozoic, and Cenezoic (then divided into periods)
radiometric dating
based on the measurement of certain radioactive isotopes in objects
half-life
the number of years it takes for 50 percentof the original sample to decay
continental drift
landmasses on different plates change position relative to each other as a result of this movement
mass extinctions
the fossil record reveals that Earth's history has long periods of relative stability broken up by comparitively brief episodes of great species loss
taxonomy
involves the identification, naming, and classification of species
binomial
a two-part name to each species
phylogenetic tree
the group that species are classified in (groups in groups)
kingdom, phylum, class, order, family, order, family, genus, species
convergent evolution
a process in which unrelated species from similar environments have adaptations that seem very similar
analogous structures
similar adaptation that result from convergent evolution
clade
each evolutionary branch in a phylogenic tree
derived characteristics
unique features that unite the organisms as a clade
cladogram
a phylogenic diagram that specifies the derived characters of clades
five-kingdom system
monerans, protists, plants, fungi, animals
three domain system
bacteria, archaea, eukaryotes
embryo sac
the resulting structure of the 3 cycles of mitosis-female gametophyte
pollination
pollen grains released from anthers land on the stigmata of flowers of the same species
pollen tube
once the pollen is on a stigmata, a pollen grain absorbs water and extends a structure-this structure grows toward the ovary through the sytle
dicot adaptation
hooked shoot tip that protects the delicate shoot by holding it downward as shoot moves through the soil
monoct adaptation
a sheath surrounding the shoot pushes straight upward \, breaking through the soil
secondary growth
growth in plant width
primary growth
growth in plant length
vascular cambium
a cylinder of actively dividing cells located between the xylem and the phloem
wood
the secondary xylem that is laid down in the growing seasons of each year accumulates as this
cork cambium
a meristem that develops from parenchyma cells in the remaining cortex
bark
everything outside the vascular cambium
nitrogen
(Function in plant) protein and nucleic acid synthesis
sulfur
(FIP) protein synthesis
phosphorus
(FIP) nucleic acid and ATP synthesis
potassium
(FIP) protein synthesis; regulation of osmosis
calcium
(FIP) cell wall formation; enyzyme activity
magnesium
clorophyll synthesis; enzyme activity
nitrogen fixation
certain species of soil bacteria convert atmospheric nitrogen to ammonia in this process
legumes
plants such as peas, peanuts, alfalfa, and beans that house their own nitrogen-fixing bacteria
nitrogen absorption
plants that can't absorb nitrogen need bacteria in the soil to do it- nitrogen must first be converted to ammonia ions or nitrate ions
nitrogen fixing bacteri
bacteria that converts nitrogen to ammonia
ammonifying bacteria
break down organic materials (feces & dead leaves)
nitrifying bacteria
converts ammonia ions to nitrate ions
root nodules
the legumes house their bacteria in these lumps found on the roots
root hairs
tiny outgrowths of the root's epidermal cells
root pressure
helps push water up the xylem and usually operates at night
endodermis
a layer of cells that surround the vascualr cambium
transpiration
the loss of water through the leaves due to evaporation-this generates the pull of of water up a tree
cohesion
the tendancy of molecules of the same kind to stick to one another
adhesion
the property of sticking together (as of glue and wood) or the joining of surfaces of different composition
tracheids
long cells with tapered ends
vessel elements
wider, shorter, much less tapered cells-hollow
guard cells
a pair of these cells surround each stoma open and close the stoma by changing shape
stoma
pores in the epidermis of leaves
sieve-tube members
the ploem of vascular tissue transports sucrose and other organic componds along with water-this strem of ploem sap occurs through these chains of cells
companion cells
cells alongside sieve-tube members that provide proteins and other resources
pressure-flow mechanism
water flows from where its pressure is higher to where its lower
source to sink
phloem moves sugars from where they're made to where they are used
epiphytes
a plant that grows on the surface of another plant but makes all its own food through photosynthesis
[arasite
plants that grow on other plants, but tap into the host plant's vascular tissue and steal their food
plant hormones
chemical messengers in plants
auxins
produced in the apical meristem
promote cell elongation (build up on the shaded side and stimulates growth beneath the tip)
cytokinins
stimulate cell division
produced in actively growing tissues (embyros, roots, and fruits)
gibberellins
stimulate the growth of stems by promoting cell division and cell elongation
also promote seed germination
abscisic acid ABA
during dormancy, this hormone inhibits celll division in buds and in the vascular cambium (halts primary and secondary growth during dormancy)
also promotes dormancy in seeds
also causes stomata to close
ethylene
stimulate fruit ripening
promotes "leaf drop"
thigmotropism
a change in plant growth due to touch
phototropism
the growth of a plant part toward or away from light
gravitropism
a plant's growth in respins to gravity
halophytes
salt-tolerant plants with adaptations such as salt-glands
circadian rhythm
a bioloigical cycle that occurs about every 24 hours
photoperiodism
the ability to use an environmental stimulus to time seasonal activities
short-day plants
certain plants flower in the fall or winter when the dark periods exceeds a certain length
critial night length
when the dark period exceeds a certain length
long-day plants
flower in the late spring or summer when dark periods shorten
day-neutral plant
flowers when it reaches a certain stage of maturity, regardless of the length of the day or night
phytochromes
pigmented proteins that detect sunrise and sunset
blastula
the first several cell divisions lead to an embryonic stage called a ________ that is common to all animals
consists of a single layer of cells surrounding a hollow cavity
gastrula
one side of the blastula folds inward, forming an embryonic stage
has both an outer and inner layer of cells
larva
immature form of an animal that looks different from the adult form and usually eats different food
metamorphosis
the larva undergoes a change of body form and becomes an adult
invertebrate
an animal without a backbone
vertebrate
animals with backbones
sponges
animals that lack true tissues and organs
collar cells
the inner layer of cells that line the central cavity of the sponge-have flagella
amoebocytes
wandering through the jelly-like material are cells that pick up food from the collar cells, digest it, and carry the nutrients to other cells
sessile
animals that are unable to move
cnidarians
invertebrates that have stinging cells and take food into a central body cavity
radial symmetry
an animal that has body parts arranged like pieces of a pie around an imaginary central axis
cnidocytes
specialized stinging cells used for defense and capturing prey
nematocyst
contains a coiled tubule that often has a posionous barb at the end
gastrovascular cavity
a digestive sac with one opening
polyp
a cylindrical body with tentacles radiating from one end
medusa
an umbrella-shaped from with fringes of tentacles around the lower-edge
flatworms
planarians are examples of the mostly small, leaflike or ribbon like ______
bilateral symmetry
an animal that has a mirror-image right and left sides
roundworms (nematodes)
small, cylindrical worms with somewhat pointed heads and tapered tails
complete digestive tract
a digestive tract that has two openings (mouth and anus) on opposite ends of a continuous tube
rotifer
tiny animals
annelids
earth worms and other segmented worms
means "little rings"
closed circulatory system
where the blood remains contained within vessels
acoelomates
animals that lack a body cavity
pseudocoelom
a fluid-filled body cavity in direct contact with the digestive tract
coelom
fluid-filled cavity that is completely line by tissue that originated in the embryo from mesoderm tissue
mollusk
invertebrate having a soft unsegmented body usually enclosed in a shell
mantle
an outgrowth of the body surface that drapes over the animal
radula
extends from the mouth and slides back and forth like a garden rake, scraping and scooping algae off rocks
open circulatory system
system in which blood is not always contained within a network of blood vessels
gastropods
snails and slugs-can live on land or in water
bivalves
animals that have hinged shells divided into 2 halves
cephalopods
ocean dwelling mollusks whose foot is adapted to form tentacles around the mouth-faster and more agile than gastropods
echinoderms
animals that lack body segments, and in most adult forms the external parts of the animal radiate from the center like the spokes of a wheel
endoskeleton
a hard internal skeleton
water vascular system
a network of water-filled canals
tube feet
branches of water vascular system that function in locomotion, feeding and respiration
protosomes
mollusks, annelids, athropods
deutrostomes
echinoderms, chordates
Cambrian explosion
a burst of animal diversity
arthropods
animals with segmented bodies, jointed appendages, and a hard exoskeleton
thorax
the midsection of athropods
jointed appendages
the parts attached to its segments
exoskeleton
a hard external skeleton
chitin
layers of protein mixed with polysaccharide
molting
as an arthropod grows, it must periodically shed its old exoskleton a secrete a larger one
ganglia
clusters of nerve bodies
compound eyes
eyes with many facets, each with its own lens
tracheae
chitin-lined tubes that lead from the interval parts of the body to the outside
spiracles
holes in the exoskeleton that allow the exchange of carbon dioxide and oxygen
crustaceans
lobsters, crabs, crayfish, shrimp, barnacles, and others
arachnids
spiders, scorpions, mites, and ticks
insects
beetles, ants, grasshoppers, butterflies, dragonflies, and others
myriapods
centipeds, and millipedes
cephalothorax
the fused head and thorax
chelicerae
fang-like mouth parts used to paralyze prey with poison
pedipalps
mouth parts used to manipulate prey once it has been paralyzed
malpighian tubules
excretory structures that remove wastes from the fluid in the body cavity
book lungs
contain many flaps that provide a large surface area for gas exchange
spinnerets
silk that is spun into fibers by organs near the end of the abdomen
carapace
the portion of the exoskeleton that covers the back of the cephalothorax forms a shield
mandibles
the mouth parts closest to the mouth tha bite and grind food
incomplete metamorphosis
the change from juvenile to adult that is not very dramatic
entomology
the study of bugs
biological control
the control of pest organisms by interfering with their natural ecological environments
central nervous system (CNS)
the body's main processing center
peripheral nervous system (PNS)
delivers info to the CNS and carries messages from the CNS to other organs through communication lines called nerves
nerve
consists of neuron fibers surrounded by connective tissue
communication lines
stimulus
info about an external environment change
sensory neurons
neurons that carry info about the stimulus to the CNS
sensory receptors
stimuli are recieved by highly specialized cells
interneurons
neurons that interpret the info about a stimulus
motor neurons
neurons that carry signals away from the CNS such as a muscle to contract
reflex
a rapid automatic response
dendrites
fibers that recieve signals and carry them toward the neuron's cells body
axon
a fiber that carries electrical impulses away from the cell body and toward other cells
myelin sheath
the axonis insulated by this thick coating material
nodes
the space between the myelin sheath
resting potential
the voltage across the plasma membrane of a resting neuron
depolarization
the chrage swithces across the membrane (positive-negative and vice-versa)
threshold
the stimulus must be strong enough to depolarize the membrane to a certain level
action potential
a stronger depolarization that is the start of the nerve signal
synapse
the junction between the axon's knobs and another cell
synaptic cleft
a tiny space between the axon's knobs and another cell
neurotransmitters
small, nitrogen-containing organic compounds
somatic nervous system
carry signals from the CNS to the skeletal muscles (mostly voluntary actions)
voluntary actions
actions under your concious control
involuntary actions
actions not under your voluntary control
autonomic nervous system
carries signals to organs such as the intestines, heart, and glands
involuntary
sympatheitc division
increases the general level of activity in the body and makes more energy available
parasympathetic divison
calms the body and returns it to regular maintenance functions
spinal cord
processes the certain types of sensory info and sends out responses via motor neurons -also contains neurons that convey signals to and from the brain
cerebrum
largest and most complex part of the brain
left hemisphere-controls right side body movements
right hemisphre-control left side body movements
corpus callosum
supports communication between the hemispheres
cerebral cortex
the outer region of the cerebrum-divided into several lobes that control different functions of the body
cerebellum
coordination center for movements-recieves signals from the cerebum indicating a need to move
brainstem
divided into 3 parts (medulla oblongata, pons, and midbrain) filters all the info from the sensory and motor neurons going to and from the brain-also regulates sleep, control breathing, and helps coordinate body movements
thalamus
sorts info going to and coming from the cerebral cortex
hypothalamus
regulates body temp, blood pressure, hunger, thirst, and emotions
limbic system
the connection between memory, emotions, and senses are part of this system
sensation
an awareness of sensory stimuli
perception
meanigful interpretation of sensory data
pain receptors
sense pain
found all over body except for brain
thermoreceptors
detect heat and cold
found in the skin and certain internal organs
mechanoreceptors
sense touch, pressure, stretch, and motion
found on the skin
chemoreceptors
sense certain types of chemicals
found in the nose and on taste buds
photoreceptors
sense various wavelengths of light
found in eyes
cornea
a transparent area of the sclera where light enters the eye
iris
gives your eye color
pupil
the dark opening in the center of the iris
control how much light enters the eye
retina
the inner surface of the eye
helps to focus images
cones
detect color
rods
detect black, white, shades of gray
auditory canal
a tunnel-like opening at the beginning of the ear
eardrum
a sheet of tissue that sepreate the outer ear from the inner ear
auditory tube
conducts air between the middle ear and the back of the throat, keeping the air pressure on either side of the eardrum
cochlea
a fluid-filled spiral shaped channel where vibrations are sent to the brain to be interpreted
also helps with balance
pathogens
disease causing organisms or viruses
infectious diseases
diseases caused by pathogens
nonspecific defense
barriers that don't distinguish one invader from another
macrophage
WBC that eat pathogens
neutrophils
WBC that eat and send chemicals into the invader
also kills WBC
Natural killers (NK)
WBC that release chemicals that poke holes in the pathogen, killing it
phagocytosis
cellular eating
inflammatory response
a nonspecific defense characterized by redness, heat, swelling, and pain
mast cells
cells that release histamine at the sight of the inflammatory site
histamine
causes nearby blood vessels to dilate (expand)
interferon
a family of proteins produced by cells in response to becoming infected by a virus
immunity
means your body is resistant is resitant to the pathogen that causes a specific disease
antigen
a large molecule, usually a protein, that provokes an immune response
antibodies
proteins found on the surface of certain WBCs, or in blood plasma, that attach to particular antigens
B cells
lymphocytes that develop in bone marrow
work with hummoral immunity
T cells
lymphocytes that develop in the thymus
work with cell-mediated immunity
plasma cell
produces and secretes antibodies specific to the antigen that activated the original B cell
humoral immunity
immunity that originates from B cells- travel in the blood and other body fluids
cell-mediated immunity
since T cells attack other cells, they produce this type of immunity
cytotoxic T cell
clones of T cells that attack cells infected with a pathogen that triggered the response
helper T cells
activated by binding to cells that display antigens in pathogens
secrete chemicals that activate both cytotoxic T cells and B cells
memory cells
long lasting lymphocytes that remember pathogens so when the pathogen attacks again, the body responds quickly
primary immune respose
first response to a pathogen attack-relatively slow and weak b/c time is needed for enough specific lymphocytes to from and defeat the pathogen
secondary immune response
second response to a pathogen attak-much stronger and faster b/c the body has developed memory cells for that specific virus/pathogen
vaccine
a dose of a pathogen or part of a pathogen that has been disabled or destroyed so it's no longer harmful
active immunity
when your body produces antibodies against an infection
passive immunity
when your body recieves antibodies from an outside source
allergy
an abnormal over-sensitivity to an otherwise unharmful antigen
allergen
an unharmful antigen that someone would be allergic to
autoimmune disease
when the immune system turns against its own molecues-can't distinguish self from non-self
AIDS
acquired immune deficiency syndrom-caused by HIV, or when your T cell level gets too low
HIV
when your body destroys the helper T cells
negative feedback
feedback in opposite phase with (decreasing) the input
endocrine glands
hormones are secreted by organs of the endocrine system
hormones
chemical messengers that trigger many of the responses that maintain homeostasis
urea
ammonia combined with carbon dioxide
excretion
the removal of nitrogen-containing wastes from the body
target cells
certain cells that are equipped to respond to a particular hormone
kidneys
primary organ of the excretory system
excrete wasters and regulate water/salt balance
urine
a liquid composed of water, urea, and other wastes
ureter
tubes that carry urine to the urinary bladder
urinary bladder
sac that holds urine
urethra
a tube through which urine leaves the body
nephrons
flitering stations in the kidneys
glomerulus
a tiny ball of capillaries-fliters at the beginning of the kidneys
bowman's capsule
the filtrate that is collected in a cup-shaped portion of the nephron
dialysis
processing the blood outside the body-replacement for kidneys
hepatitis
inflammation of the liver
cirrhosis
scarring of the liver
ADH
stimulates kidneys to reabsorb water
oxytocin
stimulates uterine contractions and mammary gland cells
growth hormone
stimulates growth and metabolism
thyroid stimulating hormone
stimulates thyroid gland
ACTH
stimulates adrenal cortex
Thymosin
stimulates T cell development (immune system)
insulin
decreases blood glucose levels
glucagon
increases blood glucose levels
testosterone
supports sperm cell development and male secondary sex characteristics
melatonin
involved in day/night cycles
releasing hormone
triggers the anterior pituitary to secrete hormones
thyroxine
stimulates and maintains metabolic processes
calcitonin
lowers blood calcium levels
PTH
raises blood calcium levels
epinephrine and norepinephrine
increases blood glucose; increases metabolic processes, constrict certain blood vessels
corticosteroids
promote glucose synthesis, reduce inflammation, increase blood glucose
estrogen
stimulates uterine lining growth and development of female secondary sex chracteristics
progesterone
promotes uterine lining growth
pituitary gland
secretes hormones that influence other glands and body functions
thyroid
butterfly-shaped gland wrapped around your trachea that secrete thyroxine and calcitonin
ovaries
where egg cells are produced
follicle
a cluser of cells that surround, protect, and nourish a developing egg
oviduct
serves as a tube to the uterus
uterus
contains and protects the developing egg
cervix
connects the uterus to the vagina
vagina
recieves penis and sperm during intercourse
birth canal
mentrual flow
testes
sperm development
scrotum
house testes outside of body for better sperm development
epididymis
where sperm development is completed
semen
fluid w/ sperm that fertilizes egg
vas deferens
connecting ducts between from sperm to epididymis
penis
the male organ that transfers sperm to a female and that carries urine out of the body.
ovulation
the secondary oocyte is released when the follicle breaks during this process
ovum
mature egg cell with a haploid nucleus
ovarian cycle
cyclic changes in the ovaries
menstrual cycle
cyclic changes in the uterus
endometrium
uterus lining that breaks down during menstruation
menstruation
epithelial cells, mucus, and blood are discharged through the vagina
fertilization
when the egg and sperm cells fuse
zygote
a fertilized egg
cleavage
a rapid series of mitotic divisions
blastocyst
a ball of cells created from cleavage
trophoblast
the outer layer of cells on the blastocyst
embryo
the developing organism from 9 weeks on
implantation
the imbedding of the blastocyst into the endometrium
gastrulation
forms 3 layers of cells (ectoderm: outer-mesoderm:inner-endoderm:inner)
placenta
enables nutrients to pass from the mother to embryo
fetus
developing child from 9 weeks till birth
labor
a series of strong, rhythmic contractions of the uterus