Download ovary - Hale AP Biology

Exam Critical Concepts
Diversity and Homeostasis
Chapters 38,39,43,45,48
Stamen
Anther
Filament
Carpel
Stigma
Style
Ovary
Sepal
Petal
Receptacle
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Flowers: reproductive shoots of plants
Receptacle: attaches flower to the stem
Flowers consist of four floral organs:
◦ Sepals: leaf like cover to flower bud
◦ Petals: Attracts insects
◦ Stamens: Male reproduce structures consists of
Filament is a stalk topped by an anther with
◦ Carpels: Female reproductive structures made of
Style holds up a stigma on which pollen lands
ovary at base containing one or more ovules
pistil a group of fused carpels
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Pollination: transfer of pollen from an anther to a
stigma
◦ can be by wind, water, bee, moth and butterfly,
fly, bird, bat, or water
Pollen develops from microspores within
the microsporangia, or pollen sacs of anthers
Pollen grain produces a pollen tube that grows
down into the ovary and discharges sperm near the
embryo sac
Within an ovule, megaspores are produced by
meiosis and develop into embryo sacs
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After landing on a stigma, a pollen grain
produces a pollen tube that extends
between the cells of the style toward the
ovary
Double fertilization results from the
discharge of two sperm from the pollen
tube into the embryo sac
One sperm fertilizes the egg, and the other
combines with the polar nuclei, giving rise
to the triploid (3n) food-storing endosperm
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After double fertilization, each ovule
develops into a seed
The ovary develops into a fruit enclosing
the seed(s)
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Pollination: the transfer of pollen from an anther to
a stigma
• can be by wind, water, bee, moth and butterfly,
fly, bird, bat, or water
Pollen tube: After landing on a stigma, a pollen
grain produces a tube which extends between the
cells of the style toward the ovary
Double fertilization: the discharge of two sperm
from the pollen tube into the embryo sac
• One sperm fertilizes the egg
• other combines with the polar nuclei, giving rise
to the triploid (3n) food-storing endosperm
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After double fertilization, each ovule develops into
a seed
The ovary develops into a fruit enclosing the
seed(s)
Endosperm development usually precedes embryo
development
Monocots and some eudicots: endosperm stores
nutrients that can be used by the seedling
Eudicots: food reserves of the endosperm are
exported to the cotyledons
Seed coat: food supply are enclosed by a hard
protective covering
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Seed dormancy: increases the chances that
germination will occur at a time and place most
advantageous to the seedling
◦ breaking of seed dormancy often requires
environmental cues, such as temperature or
lighting changes
Imbibition: uptake of water due to low water
potential of the dry seed breaks dormancy
• The radicle (embryonic root) emerges first
• Next, the shoot tip breaks through the soil
surface
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Fruit: develops from the ovary
◦ protects the enclosed seeds
◦ aids in seed dispersal by wind or animals
◦ Classified as:
 Dry: the ovary dries out at maturity
 Fleshy: the ovary becomes thick, soft, and sweet
at maturity
Fruits are also classified by their development:
◦ Simple: single or several fused carpels
◦ Aggregate: single flower with multiple separate
carpels
◦ Multiple: group of flowers called an inflorescence
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Fruit dispersal mechanisms include:
◦ Water
◦ Wind
◦ Animals
Genetically modified plants may increase the
quality and quantity of food worldwide
Transgenic crops have been developed that:
– Produce proteins to defend them against insect
pests
– Tolerate herbicides
– Resist specific diseases
Signaling in plants follow the basic steps as all
cellular responses:
1. Reception: plants have cellular receptors that
detect changes in their environment
◦ For a stimulus to elicit a response, certain cells
must have an appropriate receptor
2. Transduction: stimulation of the receptor initiates
a specific signal transduction pathway
3. Response: regulation of cellular activity
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Hormones: chemical signals that coordinate
different parts of an organism
◦ control plant growth and development by
affecting the division, elongation, and
differentiation of cells
◦ produced in very low concentration, but a minute
amount can greatly affect growth and
development of a plant organ
Tropism: any response resulting in curvature of
organs toward or away from a stimulus is called a
often caused by hormones
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Auxin: One of the most common plant hormone
◦ Promotes elongation of coleoptiles
◦ Auxin transporter proteins move the hormone
from the basal end of one cell into the apical end
of the neighboring cell
◦ Involved in root formation and branching
◦ stimulates proton pumps in the plasma
membrane
 Expansins: lower the pH in the cell wall,
activating, enzymes that loosen the wall’s fabric
 With the cellulose loosened, the cell can
elongate
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Cytokines: named because they stimulate
cytokinesis
◦ produced in actively growing tissues such as
roots, embryos, and fruits
◦ work together with auxin to control cell division
and differentiation
◦ Cytokinins, auxin, and other factors interact in
the control of apical dominance, a terminal bud’s
ability to suppress development of axillary buds
◦ If the terminal bud is removed, plants become
bushier
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Gibberellins: have a variety of effects,
◦ stimulate cell elongation and cell division in
stems
◦ in many plants, both auxin and gibberellins must
be present for fruit to set
◦ are used in spraying of Thompson seedless
grapes ( so they a seedless)
◦ after water is imbibed, release of gibberellins
from the embryo signals seeds to germinate
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Brassinosteroids: are chemically similar to the sex
hormones of animals
◦ induce cell elongation and division in stem
segments
Abscisic Acid (ABA): slows growth
◦ Causes Seed dormancy
 Seed dormancy ensures that the seed will
germinate only in optimal conditions
 In some seeds, dormancy is broken when ABA is
removed by heavy rain, light, or prolonged cold
◦ primary internal signal that enables plants to
withstand drought
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Ethylene: Hormone produced in response to
stresses such as drought, flooding, mechanical
pressure, injury, and infection
◦ Effects include response to mechanical stress,
leaf abscission, and fruit ripening
◦ Ethylene induces the triple response, which
allows a growing shoot to avoid obstacles
Senescence: programmed death of plant cells or
organs
Apoptosis: programmed destruction of cells,
organs, or whole plants
Leaf Abscission: Causes leaf drop
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Light cues many key events in plant growth and
development
Photomorphogenesis: effects of light on plant
morphology
◦ Plants detect not only presence of light but also
its direction, intensity, and wavelength (color)
◦ Action spectrum depicts relative response of a
process to different wavelengths
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Circadian Rhythm: cycles that are about 24 hours
long and are governed by an internal “clock”
◦ can be entrained to exactly 24 hours by the
day/night cycle
◦ The clock may depend on synthesis of a protein
regulated through feedback control and may be
common to all eukaryotes
Photoperiod: the relative lengths of night and day,
is the environmental stimulus plants use most
often to detect the time of year
Photoperiodism: physiological response to
photoperiod
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Herbivory: animals eating plants
◦ a stress that plants face in any ecosystem
◦ Plants counter excessive herbivory with physical
defenses such as thorns and chemical defenses
such as distasteful or toxic compounds
◦ Some plants even “recruit” predatory animals that
help defend against specific herbivores
◦ Plants damaged by insects can release volatile
chemicals to warn other plants of the same
species
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Acquired immunity, or adaptive immunity, develops
after exposure to agents
Innate immunity: present before any exposure
◦ effective from the time of birth is nonspecific
◦ consists of external barriers plus internal cellular and
chemical defenses
Barriers: include the skin and mucous membranes of the
respiratory, urinary, and reproductive tracts
◦ Mucus traps and allows for the removal of microbes
◦ fluids including saliva, mucus, and tears are hostile to
microbes
◦ The low pH of skin and the digestive system prevents
growth of microbes
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White Blood cells: engulf pathogens in the body
then fuses with a lysosome to destroy the microbe
types of phagocytic cells:
◦ Neutrophils engulf and destroy microbes
◦ Macrophages are part of the lymphatic system
and are found throughout the body
◦ Eosinophils discharge destructive enzymes
◦ Dendritic cells stimulate development of acquired
immunity
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Inflammatory response : Following an injury, mast
cells release histamine, which promotes changes in
blood vessels
◦ These changes increase local blood supply and
allow more phagocytes and antimicrobial proteins
to enter tissues
◦ Pus, a fluid rich in white blood cells, dead
microbes, and cell debris, accumulates at the site
of inflammation
◦ can be either local or systemic
(throughout the body)
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Fever: a systemic inflammatory response triggered
by pyrogens released by macrophages, and toxins
from pathogens
Septic shock: a life-threatening condition caused
by an overwhelming inflammatory response
Natural killer (NK) cells: Attack Cancerous or
infected cells that on longer express the protein,
MHC protein on their surface
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Acquired immunity: Immunity from infection or
exposure to the pathogen
◦ Lymphocytes or White blood cells: recognize and
respond to antigens, foreign molecules
◦ Lymphocytes that mature in the thymus are called
T cells, and those that mature in bone marrow
are called B cells
◦ Lymphocytes contribute to immunological
memory
◦ Cytokines:secreted by macrophages and dendritic
cells to recruit and activate lymphocytes
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Antigen: any foreign molecule to which a
lymphocyte responds
◦ A single B cell or T cell has about 100,000
identical antigen receptors
The first exposure to a specific antigen represents
the primary immune response
During this time, effector B cells called plasma cells
are generated, and T cells are activated to their
effector forms
In the secondary immune response, memory cells
facilitate a faster, more efficient response
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Active immunity: develops naturally in response to
an infection
can also develop following immunization, also
called vaccination
In immunization, a nonpathogenic form of a
microbe or part of a microbe elicits an immune
response to an immunological memory
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Passive immunity: provides immediate, short-term
protection that is conferred naturally when IgG
crosses the placenta from mother to fetus or when
IgA passes from mother to infant in breast milk
◦ It can be conferred artificially by injecting
antibodies into a nonimmune person
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MHC molecules: different among genetically
nonidentical individuals
◦ Differences in MHC molecules stimulate rejection
of tissue grafts and organ transplants
◦ Immunosuppressive drugs facilitate
transplantation
◦ Lymphocytes in bone marrow transplants may
cause the donor tissue to reject the recipient
Allergies: exaggerated (hypersensitive) responses
to antigens called allergens
◦ allergies such as hay fever, IgE antibodies
produced after first exposure to an allergen
attach to receptors on mast cells
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The next time the allergen enters the body, it binds
to mast cell–associated IgE molecules
Mast cells release histamine and other mediators
that cause vascular changes leading to typical
allergy symptoms
An acute allergic response can lead to anaphylactic
shock, a life-threatening reaction that can occur
within seconds of allergen exposure
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Autoimmune diseases: the immune system loses
tolerance for self and turns against certain
molecules of the body
◦ diseases include
 systemic lupus
 rheumatoid arthritis
 diabetes mellitus
 multiple sclerosis
Some viruses may remain in a host in an inactive
state called latency
Herpes simplex viruses can be present in a human
host without causing symptoms
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The frequency of certain cancers increases when
the immune response is impaired
Two suggested explanations are
◦ Immune system normally suppresses cancerous
cells
◦ Increased inflammation increases the risk of
cancer
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Communication in animals include:
Endocrine system: secretes hormones that
coordinate slower but longer-acting responses
including reproduction, development, energy
metabolism, growth, and behavior
◦ Chemical signals bind to receptor proteins on
target cells
◦ Only target cells respond to the signal
Nervous system: conveys high-speed electrical
signals along specialized cells called neurons;
these signals regulate other cells
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Hormones: Chemical secreted into extracellular
fluids and travel via the bloodstream
◦ mediate responses to environmental stimuli and
regulate growth, development, and reproduction
Endocrine glands: ductless and secrete hormones
directly into surrounding fluid
Local Regulators: are chemical signals that travel
over short distances by diffusion
regulate blood pressure, nervous system function,
and reproduction, divided into two types
◦ Paracrine: act on cells near the secreting cell
◦ Autocrine: act on the secreting cell itself
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Neurotransmitters: secreted chemical signals that
diffuse a short distance to bind to receptors and
play a role in sensation, memory, cognition, and
movement
Neurohormones: a class of hormones that originate
from neurons in the brain and diffuse through the
bloodstream
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Pheromones: are chemical signals that are released
from the body and used to communicate with other
individuals in the species
◦ mark trails to food sources, warn of predators,
and attract potential mates
Three major classes of molecules function as
hormones in vertebrates:
1. Polypeptides (proteins and peptides)
2. Amines derived from amino acids
3. Steroid hormones
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Epinephrine: a hormone that has multiple effects in
mediating the body’s response to short-term
stress
◦ binds to receptors on the plasma membrane of
liver cells
◦ This triggers the release of messenger molecules
that activate enzymes and result in the release of
glucose into the bloodstream
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The same hormone may have different effects on
target cells that have:
◦ Different receptors for the hormone
◦ Different signal transduction pathways
◦ Different proteins for carrying out the response
A hormone can also have different effects in
different species
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Types of local regulators:
◦ Cytokines and growth factors
◦ Nitric oxide (NO)
◦ Prostaglandins: help regulate aggregation of
platelets, an early step in formation of blood clots
Negative Feedback: inhibits a response by reducing
the initial stimulus
◦ regulates many hormonal pathways involved in
homeostasis
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Control of blood sugar: A case study in
Homeostasis:
◦ Insulin and glucagon are antagonistic hormones
that help maintain glucose homeostasis
◦ The pancreas has clusters of endocrine cells
called islets of Langerhans
 Alpha cells: produce glucagon
 Beta cells: produce insulin
Insulin: reduces blood glucose levels by:
◦ Promoting the cellular uptake of glucose
◦ Slowing glycogen breakdown in the liver
◦ Promoting fat storage
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Glucagon:increases blood glucose levels by
◦ Stimulating conversion of glycogen to glucose in
the liver
◦ Stimulating breakdown of fat and protein into
glucose
Diabetes Mellitus: is perhaps the best-known
endocrine disorder
◦ caused by a deficiency of insulin or a decreased
response to insulin in target tissues
◦ marked by elevated blood glucose levels
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Type I (insulin-dependent): is an autoimmune
disorder in which the immune system destroys
pancreatic beta cells
Type II (non-insulin-dependent): involves insulin
deficiency or reduced response of target cells due
to change in insulin receptors
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Neurons: nerve cells that transfer information
within the body
◦ Two types of signals to communicate:
1. Electrical signals (long-distance)
2. Chemical signals (short-distance)
Ganglia: simple clusters of neurons
Brain: more complex organization of neurons
Process information with three stages or types:
1. sensory neurons: detect external stimuli
2. Interneurons : integrate the information
3. motor neurons: trigger muscle or gland activity
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Many animals have a complex nervous system
which consists of:
◦ A central nervous system (CNS) where integration
takes place; this includes the brain and a nerve
cord
◦ A peripheral nervous system (PNS), which brings
information into and out of the CNS
Most of a neuron’s organelles are in the cell body
Most neurons have dendrites, highly branched
extensions that receive signals from other neurons
The axon is typically a much longer extension that
transmits signals to other cells at synapses
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Synapse: junction between an axon and
another cell
Synaptic terminal: one axon passes
information across the synapse in the form
of chemical messengers called
neurotransmitters
Most neurons are nourished or insulated by
cells called glia
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Membrane potential: difference in electrical charge
across its plasma membrane
◦ Messages are transmitted as changes in
membrane potential
Resting potential: the membrane potential of a
neuron not sending signals
◦ The concentration of K+ is greater inside the cell,
while the concentration of Na+ is greater outside
the cell
◦ Sodium-potassium pumps use the energy of ATP
to maintain these K+ and Na+ gradients across
the plasma membrane
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The opening of ion channels in the plasma
membrane converts chemical potential to electrical
potential
A neuron at resting potential contains many open
K+ channels and fewer open Na+ channels; K+
diffuses out of the cell
Anions trapped inside the cell contribute to the
negative charge within the neuron
In a resting neuron, the currents of K+ and Na+ are
equal and opposite, and the resting potential
across the membrane remains steady
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The speed of an action potential increases with the
axon’s diameter
Myelin sheath: insulated axons which causes an
action potential’s speed to increase
Neurotransmitters: Chemical signal across the
synapse
◦ can produce different effects in different types of cells
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There are five major classes of neurotransmitters:
acetylcholine, biogenic amines, amino acids,
neuropeptides, and gases
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Acetylcholine: common neurotransmitter in
vertebrates and invertebrates
◦ it is usually an excitatory transmitter
Biogenic amines: These neurotransmitters include:
◦ Epinephrine
◦ Norepinephrine
◦ Opamine
◦ serotonin
They are active in the CNS and PNS
Gas Neurotransmitters: nitric oxide and carbon
monoxide are local regulators in the PNS
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Two amino acids are known to function as major
neurotransmitters in the CNS:
◦ Gamma-aminobutyric acid (GABA)
◦ Glutamate
Neuropeptides: Neurotransmitter made of
relatively short chains of amino acids
◦ Substance P:affect our perception of pain
◦ Endorphins: affect our perception of pain
◦ Opiates bind to the same receptors as endorphins
and can be used as painkillers