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Biology AML NMAT Reviewer
Medical Technology (Far Eastern University)
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BIOLOGY
It is the study of life; the science of living organisms including its structure, composition, function, and development.
CELL – the basic structural and functional unit of an organism.
CELL COMPONENTS
1. Plasma membrane – separates the cell from its surrounding; a barrier.
2. Cytoplasm – thick fluid filling inside the cell.
3. Organelles – cellular structures suspended in the cytoplasm performing its unique and specific functions.
4. Genetic material – contains the biological information; the hereditary materials.
CELL TYPE
1. Prokaryotic cell – lacking a true nucleus and other membrane-enclosed organelles of the eukaryotic cell. It
appears simpler in structure. Prokaryotes include bacteria and archae.
2. Eukaryotic cell – means “true nucleus”. Generally much larger and more complex than prokaryotic cells. It
includes protists, fungi, animal, and plant cells.
CELL ORGANELLES AND ITS FUNCTIONS
1. Plasma membrane – functions as a selective barrier that allows the passage of enough oxygen, nutrients, and
wastes to the cell.
a. Fluid Mosaic Model – theory explaining how cell membranes are constructed.
 Molecules of the cell membrane are arranged in sheet
 The mosaic of molecules is fluid, that is, the molecules are able to float around slowly
 This model illustrates that molecules of the plasma membrane form a continuous sheet
 Chemical attractions are the forces that hold membranes together
b. Primary structure of the plasma membrane is a double layer of phospholipid molecules.
 Heads are hydrophilic (water-loving)
 Tails are hydrophobic (water-fearing)
 Cholesterol molecules are scattered among the phospholipids to allow membrane to function
properly at body temperature
c. Membrane proteins – helps the cell to maintain balance or homeostasis.
 Intrinsic protein – are inside the plasma membrane; integral protein
 Extrinsic protein – are on the peripheral side or the outside of the plasma membrane
2. Nucleus – contains DNA (hereditary material).
3. Nuclear envelope or membrane – double phospholipid bilayer that surrounds the nucleus and has pores for the
RNA to move out.
4. Nucleolus – it is where rRNA is transcribed and the subunits of ribosomes are assembled.
5. Chromosomes – part of the nucleus which is distinct during reproduction.
6. Centrioles – involved during cell division in animal cell; function in production of flagella and cilia but not
microtubule.
7. Centrosome – non-membranous structure involved in cell division; coordinates the building and breaking of
microtubules in the cell; its general location is defined by the location of the centrioles.
8. Rough Endoplasmic Reticulum – is ribosome-studded. It produces proteins.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Smooth Endoplasmic Reticulum – lipids and carbohydrates synthesis as well as drug detoxification.
Ribosome – a non-membranous structure which makes proteins.
Golgi apparatus – modifies and packages proteins.
Lysosomes – the cell’s digestive system; it contains hydrolytic enzymes.
Peroxisomes – small membranous sacs containing enzyme that detoxify harmful substances that enter the cell.
Mitochondria – the powerhouse of the cells; mitochondrial enzymes catalyze series of oxidation reaction that
provide about 95% of cell’s energy supply.
Chloroplast – present only in plants and protozoans; contains chlorophyll pigments that are responsible for
photosynthesis.
Central vacuole – prominent organelle in older plant cell; responsible for storage, breakdown of waste products,
and hydrolysis of macromolecules.
Cell wall – outer covering which maintains cell shape and protect cell from mechanical damage; made of
cellulose, other polysaccharides, and proteins.
Cytoskeleton – network of filaments responsible for the structure, transport, and cell motility.
a. Microfilaments – help in cell movement from within; the contractile force in microvilli and muscle;
squeeze membrane together in phagocytosis and cytokinesis.
b. Intermediate filaments – provide structural support.
c. Microtubules – involved in flagella and cilia construction and spindle apparatus it also help in
transporting substances to the cells.
Cell extension
a. Microvilli – found in the epithelial cells that line the intestines and other areas where absorption is
important; helps to increase cell’s surface area.
b. Cilia and Flagella – locomotion organelles.
CELL CONNECTIONS
1. Desmosomes – “spot welds” that hold adjacent cells together; fibers on the outer surface of each desmosome
interlock with each other; anchored internally by intermediate filaments of the cytoskeleton.
2. Gap junctions – membrane channels of adjacent plasma membranes adhere to each other.
3. Tight junctions – occur in cells that are joined by “collars” of tightly fused material; molecules cannot permeate
through the cracks of tight junctions.
CELL TRANSPORT
1. Passive Transport – do not require any energy utilization of the plasma membrane.
a. Diffusion – movement of molecules from greater concentration to an area of lower concentration.
b. Dialysis – a form of diffusion in which selective permeable nature of membrane causes separation of
smaller solute particles from larger solute particles.
c. Osmosis – diffusion of water through a selectively permeable membrane; limits the diffusion of at least
some of the solute particles.
 Osmotic pressure – water pressure that develops as a result of osmosis.
 Potential osmotic pressure – is the maximum pressure that could develop in a solution when it is
separated from pure water by a selectively permeable membrane.
 Hypertonic solution – has higher solute (higher pressure); cells placed in solution that are
hypertonic to intracellular fluid always shrivel (shrink or crenate) as water flows out of the cell.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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 Hypotonic solution – has a lower concentration of solute (lower pressure) than the concentration
inside the cell which causes the cell to swell as water flows into the cell.
 Isotonic solution – has a concentration equal to the concentration inside the cell.
d. Facilitated diffusion – a special kind of diffusion when movement of molecules is made more efficient
by the action of carrier mechanisms in a cell membrane. It transports substances down a concentration
gradient.
2. Active Transport – it requires energy; carrier-mediated process that moves substances against its concentration
gradient.
a. Endocytosis – the process in which the edges of the plasma membrane fuse to form a vesicle.
 Phagocytosis – cells engulf organisms or parts thereof. Example, white blood cells engulf bacteria.
 Pinocytosis – the liquid material brought into the cell containing dissolved molecules.
b. Exocytosis – is the extrusion of materials from a cell via vesicles; the reverse of endocytosis.
CELL CYCLE
1. Interphase
a. G1 or Gap 1 phase – the longest stage; proteins and mRNA are synthesized, cells split and grow.
b. S or Synthesis phase – DNA replication occurs when each chromosome replicates to produce sister
chromatids.
c. G2 or Gap 2 phase – cell prepares to divide as other organelles are replicated, chromosomes begin to
condense, and microtubules are synthesized.
2. M phase or the Division of Nucleus
a. Mitosis – cells division begins to occur.
b. Meiosis – type of cell division responsible for sex cells formation; resulting to four (4) daughter cells.
3. C phase or the Cytokinesis – the actual division of the cytoplasm producing two (2) daughter cells.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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SUMMARY
PROPERTY
MITOSIS (occurs in diploid and haploid cells)
MEIOSIS (can only occur in diploid cells)

DNA replication
Occurs during interphase before mitosis begins
Occurs during interphase before meiosis I begins

Number of
divisions
One, including prophase, prometaphase,
metaphase, anaphase, and telophase
Two, each including prophase, metaphase, anaphase,
and telophase

Synapsis of
homologous
chromosomes
Does not occur
Occurs during prophase I along with the crossing over
between non sister chromatids; resulting chiasmata
hold pairs together due to sister chromatid cohesion

Number of
daughter cells
and genetic
composition
Two, each genetically identical to the parent cell,
with the same number of chromosomes
Four, each haploid (n); genetically different from the
parent cell and from each other
Enables multicellular animal or plant
(gametophyte or sporophyte) to arise from a
single cell; produces cells for growth, repair, and
in some species, asexual reproduction; produces
gametes in the gametophyte plant
Produces gametes (in animals) or spores (in the
sporophyte plant); reduces number of chromosome
sets by half and introduces genetic variability among
the gametes or spores
 Role in the
animal or plant
body
GENE EXPRESSION AND THE CENTRAL DOGMA
1. Genes – provide instructions for making specific proteins.
2. Nucleic acid – basic building block of DNA or RNA.
3. Protein – macronutrient; made up of amino acids.
4. DNA – deoxyribonucleic acid; the hereditary material; has deoxyribose sugar; double stranded consisting of
nitrogenous bases (A T C G) and hydrogen bonds.
5. RNA – ribonucleic acid; chemically similar to DNA except that it contains ribose instead of deoxyribose sugar and
has the nitrogenous base Uracil instead of Thymine; RNA is single-stranded.
a. mRNA – carries a genetic message from the DNA to the protein-synthesizing machinery of the cell.
b. tRNA – transfers specific amino acids to growing polypeptide chain during translation.
c. rRNA – ribosomal RNA; it always functions in association with messenger RNA and transfer RNA.
d. miRNA – micro RNA; it regulates gene expression; they are encoded from the transcribed DNA of the
genes but are not translated to proteins and is referred to as noncoding RNA.
6. Protein Synthesis: DNA – Transcription – mRNA – Translation – Protein
a. Transcription – synthesis of RNA using information in the DNA.
b. Translation – synthesis of a polypeptide using the information from the mRNA.
CELLULAR RESPIRATION – is a catabolic process by which energy is released from the breakdown of compounds into
simpler substances through the transfer of electrons during redox reactions. Has two (2) types, aerobic and anaerobic
respiration. Anabolic process, consumes energy to build complex molecules from simpler ones.
1. Anaerobic respiration – absence of O2 which results in 2 ATP/mol of glucose, example, lactic acid fermentation
and alcoholic fermentation.
a. Glycolysis – breakdown of sugar; anaerobic catabolism of glucose to pyruvic acid which occurs in the
cytoplasm.
b. Fermentation – glycolysis and reduction of pyruvate producing ethanol or lactic acid and NAD+.
2. Aerobic respiration – presence of O2 which results in net 36 ATP/mol of glucose.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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ENZYME – are globular proteins which acts as catalyst that speeds up chemical reaction; lowers energy of activation; are
not consumed or altered by the reaction; and does not alter the equilibrium.
ENZYME INHIBITION
1. Competitive inhibitors – compete with substrate by binding to the active site.
2. Noncompetitive inhibitors – bind to enzyme in area other than the active site.
3. Allosteric inhibitors – bind to enzyme and change enzyme configuration.
NEUROTRANSMITTERS – endogenous chemicals that transmit signals (chemical messengers) from a neuron to a target
cell across a synapse.
1. Acetylcholine – plays a major role in the peripheral nervous system. It is released by motor neurons and
neurons of the autonomic nervous system which plays an important role in the central nervous system in
maintaining cognitive function.
2. Dopamine – are monoamines. There are several dopamine pathways in the brain and this neurotransmitter is
involved in many functions including motor control, reward and reinforcement, and motivation.
3. Serotonin – are monoamines. Project to various parts of the nervous system. As a result, serotonin is involved in
functions such as sleep, memory, appetite, mood, and others. It is also produced in the gastrointestinal tract in
response to food.
4. Glutamate – primary excitatory transmitter in the central nervous system.
5. Gamma Aminobutyric Acid (GABA) – major inhibitory transmitter.
6. Noradrenaline (Or Norepinephrine) – are monoamines and is the primary neurotransmitter in the sympathetic
nervous system where it works on the activity of various organs in the body to control blood pressure, heart
rate, liver function, etc.
7. Histamine – the last of the major monoamines which plays a role in metabolism, temperature control,
regulating various hormones, and controlling the sleep-wake cycle, amongst other functions.
8. Endorphins – are neurotransmitters that inhibit the transmission of pain signals and promote feelings of
euphoria. These chemical messengers are produced naturally by the body in response to pain, but they can also
be triggered by other activities such as aerobic exercise. See also, Enkephalins.
PLANT HORMONES – are stimulatory (promotes effects) such as auxins, giberellins, and cytokinin. They can also be
inhibitory (suppresses or restrains an effect) in function such as abscissic acid and ethylene gas. Plants need auxin,
cytokinin, and ethylene for the growth of lateral buds.
1. Auxin – has role in coordination of growth and behavioral processes in plant life cycle.
2. Cytokinin – promotes cell division in plant roots and shoots.
3. Giberellin – regulates growth and developmental processes including stem elongation, germination, dormancy,
flowering, sex expression, enzyme induction etc.
4. Ethylene – natural plant hormone which is used to ripen fruits.
5. Abscisic acid – acts as stress hormones as it stimulates the closure of stomata; it inhibits shoot growth; it
induces seeds to synthesize storage proteins; acts as antagonists to Giberellins.
SODIUM POTASSIOM PUMP IN PLASMA MEMBRANE – keeps the cell’s resting potential by pumping out Sodium ions
(Na+) and pumping in Potassium ions (K+) with the help of ATP. An active transport, which moves ions from low
concentration to a place with a high concentration. The pump removes 3 Na+ in exchange of 2 K+, thus, outside the cell
the Na+ is high.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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BLOOD CLOTTING STAGES
1. Platelets rupture
2. Prothrombin – thromboplastin / Ca++ → Thrombin
3. Fibrinogen – thrombin → Fibrin
4. Fibrin + Erythrocytes form a hardened clot
HEMOLYSIS – hemo means blood and lysis means to burst; rupturing of erythrocytes (RBC) and the release of their
content into surrounding fluid; has a hypotonic environment.
PLASMOLYSIS – in a hypertonic solution the plasma membrane shrinks within the cell but the cell wall remains intact,
this is called plasmolysis. In a hypotonic solution, cells swell but do not burst because the cell wall can withstand high
internal pressure (turgor pressure).
BETA-OXIDATION – it is the breakdown of fatty acid molecules in mitochondria to generate acetyl-coA (coenzyme A).
TRANSAMINATION – the transfer of amino groups; chemical reaction between two molecules [amino acid containing
amine (NH2) and keto acid (=O)]. Amino acid becomes keto acid and keto acid becomes amino acid.
PENTOSE PHOSPHATE PATHWAY – process that generates NADPH (reducing agent) and breaks down Pentoses
(5 Carbon sugar). An alternative to Glycolysis. Primary role is anabolic and takes place in cytosol or in plant plastids.
VEINS VS ARTERIES
1. Veins – bring deoxygenated blood back or toward the heart.
2. Arteries – bring oxygenated blood away from the heart.
3. Pulmonary veins – carries blood with highest concentration of oxygen.
4. Renal veins – veins that drain the kidney. Connect the kidney to the inferior vena cava.
5. Pulmonary artery – carries deoxygenated blood from the heart to the lungs.
6. Hepatic portal vein – blood vessels that conduct blood from gastrointestinal tract and spleen to the liver.
THE NERVOUS SYSTEM
1. Central Nervous System (CNS) – the nerves of the brain and spinal cord; the command center.
2. Peripheral Nervous System – the nerves of the rest of the body which link the CNS with the body’s receptors
and effectors; gathers information and report it back to the CNS.
3. Autonomic Nervous System – controls the body’s involuntary activities such as heart rate, secretion of sweat.
Can be further subdivided to sympathetic and parasympathetic systems.
NEURON – the functional unit of the nervous system. With the following parts:
1. Dendrite – receives message.
2. Soma – the cell body where the nucleus is located.
3. Axon – sends message to another dendrite.
PARTS OF THE BRAIN
1. Medulla – automatically controls; the beating of heart, breathing of lungs etc.
2. Brain stem – the central core of the brain where the spinal cord enters the skull.
3. Pons – helps coordinate several other autonomic functions; helps coordinate movement.
4. Thalamus – takes in sensory information related to seeing, hearing, touching, and tasting.
If any of you lacks wisdom, let him ask God, who gives generously to all
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5. Reticular formation – network inside the brain stem essential for arousal, which may also refer to things like
sleeping, walking, pain perception.
6. Cerebrum – the grey matter with left and right hemispheres; oversee one’s ability to think, speak, and perceive.
7. Cerebellum – is responsible for non-verbal learning and memory, the perception of time, and modulating of
emotions; it controls voluntary movement like your dance moves.
8. Limbic system
a. Amygdala – two lima-bean-sized clusters of neurons involved in memory consolidation and emotion.
b. Hypothalamus – keeps the whole body steady; regulates body temperature, circadian rhythms, and
hunger, helps govern the endocrine system.
c. Hippocampus – controls the learning and memory.
d. Pituary gland – secretes many different hormones, some of which affect other glands.
DIGESTIVE PROCESS
1. Mouth – this is where digestion begins; has alpha-amylase in saliva and digests carbohydrates.
2. Esophagus – no digestion occurs only peristalsis.
3. Stomach – mixes and stores food reducing it to chyme; protein digestion begins here.
a. Mucus cells – secrete mucus
b. Chief cells – secrete pepsinogen and precursor for pepsin which begins protein digestion
c. Parietal cells – secrete HCl to lower pH of stomach and raise pH of blood; also secrete intrinsic factor
which helps ileum absorb B12
d. G cells – secrete gastrin which stimulate parietal cells to secrete HCl
4. Small intestine – 90% of absorption and digestion occurs here.
a. Duodenum
b. Jejunum
c. Ileum
5. Large intestine – water and electrolyte absorption.
a. Ascending colon
b. Transverse colon
c. Descending colon
d. Sigmoid colon
e. Rectum
f. Anus
PLANT GROWTH
1. Thigmotropism – plant moves or grows in response to touch or stimuli contact.
2. Thermotropism – plant moves in response to change in temperature.
3. Heliotropism – seasonal motion of plant parts in response to direction of the sun.
4. Geotropism – growth movement by plant in response to gravity.
5. Phototropism – growth of organisms in response to light.
 How to test if photosynthesis is taking place? Put iodine on the plant.
LANOLIN PASTE APPLICATION – protects against ravages of climate and environment; this will cause the plant to bend
toward the side without the paste.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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CAPILLARIES – tiniest blood vessels that facilitate waste exchange, nutrients, gases, and hormones between blood and
body cells; do not allow protein.
CAPILLARY EXCHANGE
 Two forces control the movement of fluid through the capillary wall: blood pressure, which tends to cause
water to move out of the capillary and osmotic pressure, which tends to cause water to move in to the
capillary. The net forces influence the fluid movement.
 At the capillary end, blood pressure is relatively low because blood has been diverted from the arterial to many
capillaries; osmotic pressure is relatively high; solute concentration is still high because food has been pushed
out to the tissues of the arterial end.
 At the arterial end, blood is in high pressure because it just came from the heart; blood pressure is higher than
osmotic pressure of the blood; fluid is forced out of the blood leaving solutes behind which increases the solute
concentration of the blood as fluid moves out.
 Transcapillary flow – blood pressure exceeds the plasma osmotic pressure.
SHORT DAY PLANTS VS LONG DAY PLANTS
1. Short - day – flower when day lengths are less than the critical photoperiod. If this amount of darkness is
interrupted by a flash of light, no matter how short, the short-day plant will not flower.
2. Long - day – flower when the day length exceeds their critical photoperiod. It also flowers if the critical length of
darkness is longer than usual but is interrupted even by the shortest flash of light.
HORMONES
1. Anterior Pituitary
a. Follicle - stimulating – follicle maturation; spermatogenesis.
b. Luteinizing – ovulation; testosterone synthesis.
c. Adrenocorticotropic (ACTH) – stimulates adrenal cortex to make or secrete glucocorticoids.
d. Thyroid – stimulating; stimulates thyroid to make hormones.
e. Prolactin – stimulates milk production and secretion.
f. Endorphins – inhibit perception of pain.
g. Growth hormone – bone and muscle growth.
2. Hypothalamus store in posterior pituitary
a. Oxytocin – uterine contraction and milk secretion.
b. Vasopressin (ADH) – water reabsorption in kidneys.
3. Thyroid
a. T3 and T4 – metabolic activity.
b. Calcitonin – decreases blood calcium level.
4. Parathyroid – increases blood calcium level.
5. Adrenal Cortex
a. Glucocorticoids – increase blood glucose level and decrease protein synthesis.
b. Mineralocorticoids – increase water reabsorption in kidneys.
6. Adrenal medulla
a. Epinephrine / Norepinephrine – increases blood glucose level and heart rate.
7. Pancreas
a. Glucagon – converts glycogen to glucose in liver and increase blood glucose.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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b. Insulin – lowers blood glucose; increase glycogen stores.
c. Somatostatin – suppresses secretion of glucagon and insulin.
8. Testes
a. Testosterone – maintains male secondary sexual characteristics.
9. Ovary or Placenta
a. Estrogen – maintains female secondary sexual characteristics.
b. Progesterone – promotes growth and maintenance of endometrium.
ECOLOGY – the study of the relationship between living organisms and the environment they live in.
STRUCTURAL COMPONENTS OF THE ECOSYSTEM
1. Abiotic component – includes the non-living, example: light, water, soil, atmosphere, temperature, etc.
2. Biotic component – includes the living organisms, example: plants, animals, fungi, bacteria, etc.
CLASSIFICATION OF ORGANISMS – is hierarchal, from general to the most specific. It is divided into different Kingdoms
(the highest level of classification), followed by Phylum, Class, Order, Family, Genus, and Species.
SPECIES – organisms that can reproduce fertile offspring with each other or with the same kind.
SPECIES RICHNESS – the number of species.
SPECIES EVENNESS – the relative abundance of species.
COMMUNITY – organized collection of interacting species.
HABITAT – the type of place where individuals of given species normally live.
NICHE – is the sum of all the activities and relationships in which individuals engage as they secure and use the resources
necessary for survival and reproduction.
POPULATION – a group of interbreeding organisms.
POPULATION ACTIVITIES
1. Survival of the fittest – predicts that one species will exploit the environment more efficiently, eventually
leading to the extinction of the other with the same niche.
2. R-selection – producing large numbers of offspring that mature rapidly with no parental care (high mortality).
3. K-selection – small number of offspring, slow maturation and strong parental care.
4. Speciation – process by which a new species is formed.
5. Adaptive radiation – occurs when several separate species arise from a single ancestral species.
6. Evolutionary bottleneck – species may face a severe crisis which will cause a shift in allelic frequencies of the
survivors of the crisis.
7. Divergent evolution – two or more groups from a single population or species become isolated from each
other and become progressively less similar through accumulation of different changes.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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8. Homologous structure – structures which arose from a common ancestral structure even if they take on very
different function as a result of divergent evolution. Example, wing of a bird and arm of human.
9. Parallel evolution – two groups which begin as single species or population and which continue to evolve
similar adaptations independently after they are separated.
10. Convergent evolution – two groups which do not originate from a common group but evolve similar
adaptations, usually as exposure to similar environments.
11. Analogous structure – are derived from unrelated ancestral structures but which acquire similar features and
functions through convergent evolution. Example, wing of a bird and wing of a butterfly.
12. Polymorphism – occurrence of distinct forms.
13. Symbiosis – relationship between two species.
a. Mutualism – beneficial for both
b. Commensalism – beneficial for one and do not affect the other
c. Parasitism – beneficial for one and detrimental to the other
SUCCESSION – series of change in an ecological community that occur over time after a disturbance.
SERAL STAGES – successional stages of an ecosystem from a disturbed unvegetated state to a climax community.
MICROSERE – terminating by the loss of identity of the habitat and without the development of a climax.
BIOMES – large naturally occurring community of flora and fauna occupying major habitat.
1. Tundra – extremely cold climate resulting to a frozen undersoil (permafrost), with few plants and animals.
2. Desert – very hot and dry with little rain.
3. Taiga – largest terrestrial biome having heavy snowfall; swampy coniferous forest of high northern latitudes.
4. Tropical rainforest – are found in the areas near the equator where rainfall is abundant and the dry season lasts
no more than a few months; considered as the richest biome in terms of the number of species.
5. Savannah / Tropical grasslands – hot and dry, mainly grass, scrub and some trees. Two distinct seasons: dry
season and seasonal rain.
OCEAN ZONES
1. Littoral – part of sea, lake or river that is close to the shore. Exposed during low tide, covered during high tide.
2. Neritic – coastal water; the belt or region of shallow water adjoining the seacoast; a well oxygenated and well
illuminated environment for marine life.
3. Pelagic – any water in a sea or lake that is neither close to the bottom nor near the shore.
4. Abyssal – depths or bed of the ocean between 4000 and 6000 meters down; total darkness, never receives
daylight; characterized by lack of nutrients.
STAGES OF DEVELOPMENT
1. Gametogenesis – formation of gametes which is classified into spermatogenesis and oogenesis.
2. Fertilization – the process of a single sperm cell combining with single egg cell to form a zygote.
a. Egg activation
 Acrosomal reaction / fast block to polyspermy
 Cortical response / slow block to polyspermy
b. Zygote formation
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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3. Cleavage – rapid, multiple rounds of mitotic cell division where the overall size of the embryo does not increase.
The developing embryo is called a blastula following completion of cleavage.
4. Gastrulation – the rearrangement (movement) of cells in the blastula to create the embryonic germ layers:
ectoderm, mesoderm, endoderm. These tissue layers will produce the tissues and organs.
5. Neurulation – formation of neural plate, neural fold, and neural tube.
6. Organogenesis – the process of organ and tissue formation through cell division and differentiation.
THE FATE OF THE THREE GERM LAYERS
Germ Layers
Description

1. Endoderm
 The innermost layer



2. Ectoderm
 The outermost layer


3. Mesoderm
 The middle layer
Fate
Forms the inner lining of the digestive tract, respiratory tube, and
organs such as pancreas, liver, gall bladder, etc.
The cells of the inner lining of the glands and the tympanic cavity.
The lining of the trachea, bronchi, alveoli of lungs, urinary bladder,
and a part of the urethra.
Forms the exoskeleton of the animal: epidermis, hair, nails, eye
lens, sebaceous glands on the skin, cornea of the eye, tooth
enamel, and the epithelium of the mouth and nose.
The neural tube develops to form: brain, spinal cord, posterior
pituitary gland, motor neurons and retina.
Gives rise to four subtypes:
a. Intermediate mesoderm – kidneys and gonads
b. Paraxial mesoderm – cartilage, skeletal muscles, dermis
c. Lateral plate mesoderm – circulatory system including the
heart, blood cells, blood vessels, spleen, wall of gut, and
wall of animal body
d. Chordamesoderm – the notochord or the primitive spine
3 BASIC MUSCLE TYPES
1. Skeletal muscles – has striated, tubular, multi-nucleated fibers; is usually attached to skeleton; is voluntary.
2. Cardiac muscles – has striated, branched, uni-nucleated fibers; occurs in walls of the heart; is involuntary.
3. Smooth muscles – non-striated, has spindle-shaped, uni-nucleated fibers; occurs in walls of internal organs; is
involuntary.
GENETICS – the scientific study of heredity and hereditary variation.
HEREDITY – the transmission of traits from one generation to the next generation, also called inheritance.
GENES – hereditary units; each gene in an organism’s DNA exists at a specific locus. Alternative versions of genes are
called ALLELES.
GAMETES – reproductive cells in animals and plants that transmit genes from one generation to the next.
ASEXUAL REPRODUCTION – a single parent produces a genetically identical offspring by mitosis. Meanwhile,
SEXUAL REPRODUCTION combines genes from two (2) parents, leading to genetically diverse offspring.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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CHARACTER – a heritable feature that varies among individuals, such as flower colors. Each variant for a character, such
as purple or white color for flowers, is called a TRAIT.
HYBRIDIZATION – mating or crossing of two true-breeding varieties. The true-breeding parents is referred to as
P generation (parental generation), and their hybrid offspring is the F1 generation (first filial generation). Allowing this
F1 hybrids to self-pollinate (or cross pollinate with other F1 hybrids) produces F2 generation. Normal human somatic
cells are diploid. They have 46 chromosomes made up of two sets of 23, one set from each parent.
Human diploid cells have 22 homologous pairs of autosomes, and one pair of sex chromosomes; the latter determines
whether the person is male (XY) or female (XX).
In humans, ovaries and testes produce haploid gametes by meiosis, each gamete set contains 23 chromosomes (n = 23).
During fertilization, an egg and sperm unite, forming a diploid (2n = 46) single-celled zygote, which develops into a
multicellular organism by mitosis.
Plants and some species of algae exhibit a second type of life cycle called alternation of generations. This type includes
both diploid and haploid stages that are multicellular.
The multicellular diploid stage is called the sporophyte while the haploid stage is called the gametophyte generation.
MENDEL’S MODEL
1. Alternative versions of genes (called alleles) account for variations of inherited characters.
2. For each character, an organism inherits two copies (that is, two alleles) of a gene, one from each parent.
3. If the two alleles at the locus differ, then one, the dominant allele, determines the organism’s appearance; the
other, the recessive allele, has no noticeable effect on the organism’s appearance.
4. The law of segregation, states that two alleles for a
heritable character segregates (separates from each other)
during gamete formation and end up in different gametes.
Mendel’s segregation model accounts for a 3:1 ratio.
PUNNETT SQUARE – a handy diagrammatic device for predicting
the allele composition of offspring from a cross between
individuals of known genetic makeup.
An organism that has two identical alleles for a character is said to
be homozygous for the gene controlling that character; they
breed-pure. While, an organism that has two different alleles for a
character is heterozygous for that gene; not true-breeding.
We distinguish an organism’s appearance based on its observable
traits, called phenotype, and its genetic makeup, genotype.
TEST CROSS – breeding an organism of an unknown genotype with
a recessive homozygote; it reveals the genotype of the organism.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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LAW OF INDEPENDENT ASSORTMENT – two or more genes assort independently; that is, each pair of allele segregates
independently of each other pair of alleles during gamete formation.
NON - MENDELIAN GENETICS
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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MUTATION – a change in the DNA of an organism which may or may not have an effect on the genotype and phenotype.
Normally, mutations are rare and random events.
ABNORMAL CHROMOSOME NUMBER
1. Nondisjunction – an ocassional mishap but ideally, the meiotic spindle distributes chromosomes to daughter
cells without error.
2. Aneuploidy – if either of the aberrant gametes unite with a normal one at fertilization, the zygote will also have
an abnormal number of a particular chromosome.
3. Monosomic – missing one copy of chromosome (2n – 1)
4. Trisomic – have one extra copy of chromosome (2n + 1)
5. Polyploidy – more than two complete sets of chromosomes; can result from complete nondisjunction during
gamete formation.
ALTERATIONS OF CHROMOSOME STRUCTURE
1. Silence mutation – causes no change in the activity of the protein.
2. Missense mutation – is a change in one DNA base pair that results in the substitution of one amino acid for
another in the protein made by gene.
3. Nonsense mutation – is also a change in one DNA base pair. Instead of substituting one amino acid for another,
the altered DNA sequence prematurely signals the cell to stop building a protein which results to a shortened
protein that may function improperly or not at all.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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4. Frameshift mutation – the addition or loss of DNA bases changes a gene’s reading frame (consists of groups of 3
bases that code for amino acid). Resulting protein is usually nonfunctional. Deletions, insertions, duplications
can all be frameshift mutations.
5. Deletion – it removes or lost a chromosomal segment.
6. Duplication – it repeats a segment; the deleted fragment
may become attached as an extra segment to a sister
chromatid.
7. Inversion – reverses a segment within a chromosome; a
chromosomal fragment may also reattach to the original
chromosome but in a reverse orientation.
8. Translocation – moves a segment from one chromosome to
a nonhomologous chromosome. In a reciprocal
translocation, the most common type, nonhomologous
chromosomes exchange fragments.
KARYOTPYE – it is the number, size, and shape of chromosomes in
an organism.
HUMAN DISORDERS DUE TO CHROMOSOMAL ALTERATIONS
1. Down syndrome (Trisomy 21) – usually the result of an
extra chromosome 21, so that each body cell has a total of
47 chromosomes; distinct facial features, short stature,
correctable heart defects, developmental delays.
2. Patau syndrome (Trisomy 13) – serious eye, brain,
circulatory defects as well as cleft palate.
3. Edward’s syndrome (Trisomy 18) – almost every organ
system affected.
4. Klinefelter syndrome – an extra chromosome in male, producing XXY; breast enlargement and other female
characteristics are common, testes are abnormally small and are sterile, taller than average.
5. Trisomy X – XXX; slightly taller than average, at risk for learning disabilities but are fertile.
6. Turner syndrome – XO and is also called Monosomy X; phenotypically female but are sterile and the sex organs
do not mature.
7. Cri du chat – deletion in chromosome 5; severely intellectually disabled, has small head, unusual facial features,
cry sounds like the mewing of a distressed cat.
If any of you lacks wisdom, let him ask God, who gives generously to all
without reproach, and it will be given him. – James 1:5
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