SCIENCE REVIEWER The Nervous System • • Highly complex part of an animal Coordinates its actions and sensory information by transmitting signals to and from different parts of its body • Detects environmental changes that impact the body • Works in tandem with the endocrine system to respond Central Nervous System • Consists of the brain and spinal cord • Controls most of the body and mind Peripheral Nervous System • Contains all the nerves that lie outside of the central nervous system • Connects the CNS to the organs, limbs, and skin • 12 pairs of cranial nerves and 31 pairs of spinal nerves Þ Somatic Nervous System • Connects the brain and spinal cord to voluntary muscles • External environment Þ Autonomic Nervous System • Connects the brain and spinal cord to involuntary muscles (heart, blood vessels, lungs, etc.) • Internal environment 2 Divisions of Autonomic Nervous System Þ Sympathetic System (SyNS) • It is activated when the body is in a dynamic role or stress • “Fight-or-flight Response” Þ Parasympathetic System (PaNS) • Maintains body functions and restores the body to normal or relaxed mode • “Rest-and-Digest Response” THE BRAIN • Controls most of the functions of the body, including awareness, movement, thinking, speech, and the 5 senses of seeing, hearing, feeling, tasting and smelling. Cerebrum • Site of intelligence of the person (perception, imagination, thought, judgment and decision) 4 Lobes of the Cerebrum Þ Frontal Lobe • Personality, emotions, higher-thinking skills Þ Parietal Lobe • Somatosensory information, attention, language Þ Temporal Lobe • Hearing, language, reading Þ Occipital Lobe • Vision, recognition of shapes and colors Limbic System Þ Hippocampus • Storage of new information in memory • Compares sensory information with what the brain expects about the world • Spatial and navigation memories Þ Amygdala • Pleasure, fear, addiction, anxiety, depression, arousal • Memories of emotional events Diencephalon Þ Thalamus • Relays sensory and motor information to the cortex • Consciousness, sleep, alertness Þ Hypothalamus • Waking up, adrenaline, water balance, appetite • Control of the pituitary gland • Control of the autonomic nervous system Glands in the Brain Þ Hypothalamus • Master of the master gland Þ Pineal Gland • Controls sleep and circadian rhythm (biological clock) Þ Pituitary Gland • Master gland • Controls growth, temperature, pregnancy and childbirth Corpus Callosum • Connects the two cerebral hemispheres Midbrain (Mesencephalon) • Coordinates sensory information with simple movements • Tectum, Tegmentum, Colliculi Colliculus (Reflex Center) Þ Superior Colliculus • Movements of the eye, head and neck response to visual stimuli Þ Inferior Colliculus • Movements of the head and trunk in response to sound stimuli Myelencephalon Þ Medulla Oblongata • Controls the heartbeat blood pressure, and reflex action (vomiting, coughing, etc.) Metencephalon Þ Cerebellum • “Little Brain” • Motor control, body coordination, spatial navigation and balance Þ Pons • Controls breathing, facial expressions, dreaming SPECIAL AREAS OF THE BRAIN Þ Cortex – surface of the cerebrum Þ Gyrus/Gyri – folds of the cerebrum Þ Sulcus/Sulci – spaces between the folds/grooves. Þ Fissure – deeper grooves than the sulci Þ Broca’s Area – responsible for producing knowledge Þ Wernicke’s Area – helps in speech processing and understanding language THE NERVE (Neurons) • Building block of the nervous system Classification 1. Location • Cranial nerves • Spinal nerves 2. Function • Sensory neuron (Afferent neuron) • Interneuron (Associative/relay neuron) • Motor neuron (Efferent neuron) Þ Afferent Neurons • Long dendrites, short axons • Cell body at the side of the neuron • Begins with a receptor Þ Efferent Neurons • Short dendrites, long axons • Cell body at the end of the neuron • Ends with an effector Neurotransmission • is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron, and bind to and react with the receptors on the dendrites of another neuron a short distance away. How does neurotransmission work? • Dendrites receive signals that come together and then the total signal is transmitted to the longest branch, the axon. The axon carries nerve impulses from a cell body to the next cell. Þ Presynaptic Neuron – transmits the signal toward a synapse Þ Action Potential – gets generated when the negative inside potential reaches the threshold Þ Neurotransmitters – chemicals that allow neurons to communicate with each other throughout the body Þ Synapse/Synaptic Space – the points of contact between neurons where information is passed from one neuron to the next Þ Postsynaptic Neuron – receives the neurotransmitter after it has crossed the synapse Þ Transport Protein – moves other materials within an organism Þ Synaptic Vesicle – central role in synaptic transmission. Stimulus-dependent release of neurotransmitter DISEASES AND DISORDERS OF THE NERVOUS SYSTEM Alzheimer’s Disease • Progressive irreversible decline in memory and a deterioration of various cognitive abilities, characterized by the destruction of nerve cells and neural connections in the cerebral cortex Coma(tose) • State of unconsciousness, characterized by the loss of reaction to external stimuli and absence of spontaneous activity Epilepsy • Sudden recurrent seizures caused by an absence or excess of signaling of nerve cells in the brain • May include convulsions, lapses of consciousness, strange movements or sensations in parts of the body, odd behaviors, and emotional disturbances Hydrocephalus • Accumulation of cerebrospinal fluid in the ventricles, or cavities of the brain, causing progressive enlargement of the head Stroke (Cerebrovascular Accident/CVA) • Sudden impairment of the brain function resulting either from a substantial reduction in blood flow to some parts of the brain or from intracranial bleeding • Consequences may include transient or lasting paralysis on one or both sides of the body. Difficulties in speaking or eating, and loss in muscular coordination. The Endocrine System • Human organ system that is made up of glands that make and secretes hormones • They carry information and instructions from one set of cells to another • Regulates how much of each hormone is released Endocrine Glands • And organ that. Makes hormones that are released directly into the blood and travel to tissues and organs all over the body Hormones • Are the body’s chemical messengers • Helps control mood, growth and development, the way our organs work, metabolism, and reproduction Endocrine Glands in the Brain Þ Pineal Gland – melatonin Þ Pituitary Gland o Anterior Pituitary – growth hormone, thyroidstimulating hormone, prolactin, adrenocorticotropic hormone, folliclestimulating hormone o Posterior Pituitary – Oxytocin, vasopressin, anti-diuretic hormone Þ Hypothalamus – dopamine, somatostatin, growth hormone-releasing hormone, gonadotropinreleasing hormone, corticotropin-releasing hormone, thyrotropin-releasing hormone Endocrine Glands in the Neck Þ Thyroid – thyroxine (T4), triiodothyronine (T3), calcitonin Þ Parathyroid – parathyroid hormone Endocrine Glands in the Chest Þ Thymus – usually not active in adulthood/releases thymosin in children Endocrine Glands in the Abdomen Þ Adrenal Glands o Adrenal Medulla – epinephrine, norepinephrine o Adrenal Cortex – glucocorticoids, mineralocorticoids Þ Pancreas - insulin Endocrine Glands in the Reproductive Organs Þ GONADS o Ovaries – estrogen, progesterone o Testes – androgen The Happiness Hormones • Hugs and kisses between humans can be used to display love, kindness, protection and lust. We generally perform these actions with people we love which, in turn, leads to the body producing a number of different hormones. Þ Dopamine – produced when we feel satisfied, resulting in feeling happy, excited, and stimulated Þ Endorphins – helps in reducing physical pain of injury in our muscles Þ Oxytocin – helps us to build bond, trust, and empathy with other human beings Þ Serotonin - helps in reducing the symptoms of depression and also regulates our mood The Human Reproductive System • organ system by which humans reproduce and bear live offspring. FEMALE REPRODUCTIVE SYSTEM The female reproductive system has the following functions: 1. Produces female sex cells (egg cells) • The egg cell/ovum is the female reproductive cell (gamete) • The egg cell is typically not capable of active movement, and it is much larger (visible to the naked eye) than the motile sperm cell. 2. Receives sperm cells from the male 3. Nurtures the development of and provides nourishment for the new individual PARTS AND FUNCTIONS Ovaries • Female reproductive organs • Almond-shaped, located on each side of the pelvic cavity • It is designed for developing the female reproductive cells – eggs of ova and producing female hormones Fallopian Tubes/Oviducts • Paired, tubular and muscular organs that run from the uterus toward the ovary • The tubal lining is covered by small, hair-like cilia so that the ovum can move slowly onward Uterus (Womb) • Site of egg implantation • Fertilized egg develops • Its upper part can be freely movable and can easily expand during pregnancy when the fertilized egg develops into an embryo, then a fetus and finally, to a fully developed infant • Endometrium – the inner lining, it is shed during the period • Myometrium – the thick middle muscle layer of the corpus of fundus. This expands during pregnancy to hold the growing baby. It contracts during labor to push the baby out. • Uterine Fundus – broad curved upper area in which the fallopian tubes connect to the uterus. Cervix • Located at the end of the uterus • It is the opening to the uterus • Cervical canal – spindle-shaped, flattened canal of the cervix, the neck of the uterus Vagina • It is the birth canal leading from the uterus to the external opening of the reproductive tract • It receives the penis of male during mating • It is covered by the external part called vulva – located between the legs Vulva • The outer part of the female genitals • Includes the opening of the vagina (vestibule), the labia majora (outer lips), labia minora (inner lips) and the clitoris Breast (Mammary Glands) • Considered accessory organs of the female reproductive system. • Supplies milk to an infant in a process called lactation. • The breast is the tissue overlying the chest (pectoral) muscles • Made of specialized tissue that produces milk (glandular tissue) as well as fatty tissue • The milk-producing part of the breast is organized into 15-20 sections, called lobes. • Lobules, where milk is produced • The milk travels through a network of tiny tubes called ducts • The ducts connect and come together into larger ducts, which eventually exit the skin in the nipple. • Areola – the dark area of skin surrounding the nipple • Connective tissue and ligaments provide support to the breast and give it its shape. Nerves provide sensation to the breast. Also contains blood vessels, lymph vessels and lymph nodes. MALE REPRODUCTIVE SYSTEM Testes • Male reproductive organ • Source of spermatozoa (sperm) and also of male sex hormones • Hangs in a body or pouch called scrotum Scrotum • Fold of skin outside the abdominal cavity which encloses the testes Seminiferous Tubules • Highly coiled tubules in the testes that produces sperm Epididymis • Temporary storage place for sperm prior to ejaculation once the sperm cells are formed in the seminiferous tubules • Ejaculation – the release of semen from the penis Vas Deferens • Receives the sperm cell from the epididymis, carries them up and delivers them to the urethra Urethra • Same tube that drains the urinary bladder • Serves as the passageway of sperm and urine to the external environment Glands • Provides liquid in which sperm can swim Þ Seminal Vesicle – secretes a fluid that makes up most of the components of the semen Þ Prostate Gland – secretes a slightly alkaline milky fluid that is discharged as part of the semen Þ Bulbourethral Gland – secretes a thick and clear mucus that lubricates and neutralizes any trace of acidic urine in the urethra Penis • It is the male organ of copulation, is partly inside and partly outside of the body • Cylindrical organ through which sperm and urine can exit the body • It transfers sperm to the female organ • Contains erectile tissue Sperm • Male reproductive cell and is derived from the Greek word sperma (meaning seed) The Menstrual Cycle • Refers to the cycle of physiological changes from the beginning of one menstrual period to the beginning of the next Menarche • First occurrence of menstruation • Occurs between the ages of 9-16 Perimenopause • Ovaries produce less estrogen and progesterone. • Hormone levels fluctuate, periods are getting irregular in length and frequency. Ovaries may or may not release an egg. • Although fertility is declining, you can still conceive. May last for several years Menopause • Point in time when menstrual cycles permanently cease due to the natural depletion of ovarian oocytes from aging • You no longer ovulate and you cannot conceive a child Post menopause • Hormone levels will never again be suitable range for ovulation and pregnancy. Birth control is no longer necessary Menstruation • Visible manifestation of cyclic physiological uterine bleeding due to shedding of the endometrium Menstrual Cycle • Refers to the cycle of physiological changes from the beginning of one menstrual period to the beginning of the next THE FOUR PHASES OF THE MENSTRUAL CYCLE Menstrual Phase (3-7 days) • Starts when an egg is not fertilized. The thickened lining of your uterus is no longer needed Follicular Phase (6-7 days) • Starts from the first day of the period overlapping with the menstrual phase until ovulation Ovulation Phase (usually occurs between 12th to 14th day) • Is the only time during cycle when you can get pregnant Luteal Phase • When the follicles release the mature ovum. The follicles change into corpus luteum releases progesterone FSH – follicle stimulating hormone LH – luteinizing hormone FERTILIZATION AND BABY GROWTH Formation of Twins Fraternal twins -> dizygotic • From two separate eggs that are fertilized by different sperms. • Hyperovulation – when the ovaries release two eggs Identical twins -> monozygotic • A single zygote splitting to form two separate embryos with identical genetic material. They have identical DNA and share a lot of physical traits. Heredity : Inheritance and Variation DNA • recipe for synthesizing protein • contains the instructions for making proteins within the cell • Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue and can also serve as a fuel source Nucleic Acids • Guanine • Adenine • Cytosine • Thymine • Uracil Chargaff’s Rule The amount of Adenine = The amount of Thymine The amount of Guanine = The amount of Cytosine DNA REPLICATION • Process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules • Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell Leading Strand • Runs from 5’ to 3’ direction, forming a continuous strand Lagging Strand • Runs from 3’ to 5’ direction, forming fragments Antiparallel • DNA is made up of two strands that is oriented in opposite directions Okazaki Fragments • Short sequences of DNA nucleotides which are synthesized discontinuously and later linked together by the enzyme DNA ligase Semiconservative • After replication, there will be two double helix DNA molecule that contain one old DNA strand and one newly made strand Enzymes Þ Topoisomerase – stops the DNA strand from supercoiling Þ Helicase – “unzipping enzyme” – unwinds the DNA Þ SSB Proteins – single-stranded binding proteins bind to the DNA strand to keep them separated after helicase unwinds it Þ RNA Primer and Primase – primer enzyme, synthesizes short RNA sequences. Stands as starting point for DNA synthesis Þ DNA Polymerase – “builder” enzymes that create DNA molecules by assembling nucleotides Þ Ligase – “gluer” facilitates the joining of the DNA strands together by catalyzing the formation of phosphodiester bond (chemical bond that forms when two hydroxyl groups in phosphoric acid react with a hydroxyl group on other molecules forming ester bonds) Errors in Protein Synthesis Types of RNA Þ mRNA – Messenger RNA • encodes amino acid sequence of a polypeptide Þ tRNA – Transfer RNA • Brings amino acids to ribosomes during translation Þ rRNA – Ribosomal RNA • With ribosomal proteins, makes up the ribosomes, the organelles that translate the mRNA Genetic Code • Chart of 64 triplets of nucleotides Codon • Sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule Anti-codon • Sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA Transcription • Process by which genetic information encoded in DNA is copied onto mRNA Translation • Process by which information encoded in mRNA is used to assemble a protein MUTATION • An alteration in the nucleotide sequence of the genome of an organism • The changing of the structure of a gene, resulting in a variant form that may be transmitted to subsequent generations • Change in a DNA sequence Causes of Mutation Þ Natural/Spontaneous Mutation – DNA copying mistakes during cell division Þ Induced – exposed to ionizing radiation, mutagens, or viral infections Types of Mutation Þ Number of DNA Sequence Involved • Small-scale (Genetic) o Change in one or more bases in the DNA sequence o Point Mutation, Frameshift, Substitution, Inversion • Large-scale (Chromosomal) o Large chunks of DNA are inserted, repeated or lost o Duplication, deletion, translocation, inversion, polyploidy, aneuploidy Þ Nature of DNA Sequence • Somatic o Mutation in body cells (error in DNA replication before mitosis) • Germline o Mutation in sex cells (error in DNA replication before meiosis) Small-scale mutation (DNA/Protein) Þ Point Mutation • Silent • Nonsense • Missense Þ Frameshift Mutation • Deletion • Insertion Þ Substitution Þ Inversion Large-scale Mutation (Chromosome) Þ Change in Chromosome Structure • Inversion • Duplication • Deletion • Insertion • Translocation Þ Change in Chromosome Number • Aneuploidy – abnormal chromosome number (extra or fewer) • Nondisjunction – the failure of homologous chromosomes to separate properly during meiosis o One less: 45 (Monosomy) o One extra: 47 (Trisomy) • Polyploidy – abnormal number of chromosome sets o 1 extra set: 3n (Triploid) o 2 extra sets: 4n (Tetraploid) *Lethal in humans, beneficial in plants Karyotype • Diagram of a complete set of chromosomes of a cell or an organism Disorders Caused by Germline Mutation Turner’s Syndrome (44-XO, 45) • Short, stocky, with broad flat chest, underdeveloped ovaries, oviducts and uterus • Low to normal intelligence, weak in math and space perception • Can live fairly normal with hormone supplements Poly-X Syndrome / Superfemale (44-XXX, 47) • Tall stature • Vertical skin folds that may cover the inner corners of the eyes (epicanthal folds) • Delayed development of speech and language skills • Weak muscle tone (hypotonia) • Curved pinky fingers (clinodactyly) • Behavior and mental health problems • Premature ovarian failure or ovary abnormalities • Constipation or abdominal pains Klinefelter Syndrome (44-XXY, 47) • Lower IQ than sibs • Tall stature • Poor muscle tone • Reduced secondary sexual characteristics • Gynecomastia (male breast) • Small testes/infertility Jacobs Syndrome / Metamale (44-XYY, 47) • Extra tallness • Defect of learning • Weak bones • Hard time speaking • Hypotonia • Small penis and testicles • Lack of the ability to grow hair on face or body • Infertility • Sex drive is decreased • Emotional problems Disorders Caused by Germline Mutation X-Linked Disorders • Color-blindness • Hemophilia • Hypertrichosis Disorders Caused by Somatic Mutation Þ Autosomal Dominant Disorder – achondroplasia, polydactyly, syndactyly, polysyndactyly, vitiligo, familial hypercholesterolemia, cri-du-chat syndrome • Males and females can be affected • Male-to-male transmission can occur • Males and females transmit their trait with equal frequency • Successive generations are affected • Transmission stops after a generation in which no one is affected Þ Autosomal Recessive Disorder – albinism, cystic fibrosis, sickle cell anemia o Trisomic Disorders – Mosaicism Syndrome (Trisomy 9), Patau Syndrome (Trisomy 13), Edward’s Syndrome (Trisomy 18), Down Syndrome (Trisomy 21) • Males and females are affected • Affected males and females can transmit the gene, unless it causes death before reproductive age • The trait can skip generation • Parents of an affected individual are heterozygous or have the trait Principles of Evolution THEORIES ON THE ORIGIN OF LIFE Oparin-Haldane Hypothesis • Aleksandr Oparin (Materialistic Theory) and JBS Haldane (Physicochemical Theory) • The origin of life on Earth is the result of a slow process of chemical evolution that probably occurred about 3.8 BYA Þ Chemical Evolution Theory • Postulates: spontaneous generation of life, under the present environmental conditions is not possible • Earth’s surface and atmosphere during the first billion years of existence, were radically different from that of today’s conditions • The primitive Earth’s atmosphere was a reducing type of atmosphere and not oxidizing type • the first-time life arose from a collection of chemical substances through a progressive series of chemical reactions • solar radiation, heat radiated by Earth and lightning must have been the chief energy source for these chemical reactions to occur *Backed-up by science Þ The Miller-Urey Experiment • Proposed by Stanley Miller and Harold Urey • Experiment which supported the theory of chemical evolution • Showed that simple organic compounds of building blocks of proteins and other macromolecules can be formed from gases with the addition of energy Spontaneous Generation (Abiogenesis) • Aristotle • Living organisms could arise suddenly and spontaneously from any kind of non-living matter Biogenesis • Louis Pasteur • All living organisms arise from pre-existing life forms Uniformitarianism (Gradualism) • James Hutton • Natural forces that are now changing the face of the Earth’s surface has been acting upon the planet since the beginning in much the same way Catastrophism • Georges Cuvier • There have been several creations of life by God, each preceded by a catastrophe resulting from some kind of geological disturbance, with each new life forms different from the previous one Panspermia (Cosmozoic) • Fred Hoyle and Chandra Wickramasinghe • Life has reached Earth from other heavenly bodies such as meteorites, in the form of highly resistant spores of some organisms Creationism • All different life forms that occur today were created by “God) THEORIES OF BIOLOGICAL EVOLUTION Evolution • All about the changes that have transformed living things from the simplest forms to the diverse organisms that exist today o continuous (but gradual) o changing o mutation Geologic Time Scale • A system of chronological dating that classifies geologic strata in time • The ‘calendar’ for events in Earth’s history o Eons o Eras o Periods o Epochs o Ages Þ Paleozoic Era: Age of Marine Life (540-252 MYA) Þ Mesozoic Era: Age of Dinosaurs (252-66 MYA) Þ Cenozoic Era: Age of Animals (66 MYA-present) Darwinism • Charles Darwin • Principle of Natural Selection o In nature, organisms with desirable traits may survive while those with weaker traits may not Þ Struggle for Existence – competition for food and space Þ Survival of the Fittest – ability of an organism to survive and produce offspring Þ Adaptation – an organism becomes better suited to its environment o Structural Adaptation – change involving a physical aspect of an organism (camouflage, mimicry, thick furs) o Physiological Adaptation – change in a species’ bodily function (feedback mechanisms, poison production, reflex actions) o Behavioral Adaptation – change affecting the way an organism naturally acts (migration, hibernation, phototropism) • Endangered o The condition of species becoming less in population • Extinct o The condition of species that perish or are gone forever Lamarckism • Jean-Baptiste De Lamarck Þ Theory of Need o Body structured develop because of the need to survive Þ Theory of Use and Disuse o Body structures develop because they are used extensively o Body structures do not develop because they are not used Þ Theory of Acquired Traits o Body structures develop to the next generation due to developed traits EVIDENCE OF BIOLOGICAL EVOLUTION Direct • Fossil records (Paleontology/Archaeology) o Earliest: Pre-Cambrian Era o Found in: Sedimentary Rocks o Types: (1) Petrified, (2) Imprints/Impressions Indirect • Comparative Anatomy – homologs, analogs, vestiges • Embryology – embryonic development of different species • Biochemistry – genomic DNA (protein similarity) • Biogeography – species distribution Worldwide Archaeopteryx Fossil • Transitional fossil between dinosaurs and birds Homologous Structures • Species having the same structure, but differ in function Analogous Structures • Species having different structure, but similar in function Vestigial Structures • Structures in the human body with no apparent use/function Common Descent/Ancestry • The more similar the Genomic DNA sequence of different species, the more that they are closely related to one another Biogeography • Study of the distribution of plants and animals to determine how and where different species migrate Theodosius Grygorovych Dobzhansky • Prominent Ukrainian-American geneticist and evolutionary biologist • Central figure in the field of evolutionary biology for his work in shaping the modern synthesis Population Ecology BIODIVERSITY • The variety of species found on Earth including the geographic locations they are found in Philippine Biodiversity Laws Þ PD 1152 – Philippine Environment Code Þ RA 9147 – Wildlife Protection Act Þ RA 8485 – Promotion of Animal Welfare in the Philippines Þ PD 389 – Forestry Reform Code Þ ACT 2590 – Protection of Game and Fish Þ RA 7900 – High-value Crops Developmental Act of 1995 Þ RA 8371 – Recognizing the Rights of Indigenous Cultural Communities/Indigenous People CATEGORIES SPECIES’ VALUE Direct Economic Value • Products are sources of food, medicine, clothing, shelter, and energy Þ Crops as food source Þ Medicinal plants Þ Fruit-bearing trees Þ Lumber Indirect Economic Value • Benefits produced by the organism without using them Þ Trees Þ Cycled materials in the soil Aesthetic Value • Provides visual or artistic enjoyment Þ Forested Landscape Þ Natural park Þ Prayer Mountains POPULATION CHANGES • Have implication on two very important concerns in maintaining the stability of an ecosystem Þ Resource consumption Þ Biodiversity conservation Population Þ Population Ecology o Inhabitants of a particular area o A group of interbreeding members of the same species Þ Demography o the total number of people living in a region or country Population Increase Þ Birth/Natality Rate o Ratio of total lice births to total population in a specified area over a specified period of time Þ Immigration o Species moving into a different location to live there Population Decrease Þ Death/Mortality Rate o Rate at which a particular species or population dies, whatever the cause Þ Emigration o Species leaving a place/region in order to live somewhere else Population Increase = (BR + IMG) – (DR + EMG) Population Growth = (Pop. Increase/Org. Population) x 100% New Population = Pop. Increase + Original Pop. Population Density • the number of organisms per unit area of place • Population Density = Pop/Land Area (km^2) FACTORS AFFECTING POPULATION GROWTH Density-Dependent • Factors that regulate population growth and influenced by population density Þ Diseases and parasites Þ Competition for resources Þ Predation Þ Migration (Emigration and Immigration) Density-Independent • Factors that do not directly influence changes in population growth Þ Natural disasters Þ Temperature Þ Sunlight Þ Human activities POPULATION GROWTH CURVE Biotic Potential • The unrestrained biological reproduction • The maximum rate at which a population could increase under ideal conditions Carrying Capacity • The maximum number of individuals of a given species supported by a given area on a sustained basis