Science 2nd Term Exam Reviewer PDF

I.​ Coordinated Functions of Endocrine, Nervous, and Reproductive System 1.​ Stimulus and Response Nervous System -​ The nervous system includes the brain, spinal cord, and a complex network of nerves. -​ This system sends messages back and forth between the brain and th...

I.​ Coordinated Functions of Endocrine, Nervous, and Reproductive System 1.​ Stimulus and Response Nervous System -​ The nervous system includes the brain, spinal cord, and a complex network of nerves. -​ This system sends messages back and forth between the brain and the body. -​ Constantly alive with electricity this is the body's prime communication and coordination network. -​ The nervous system is divided into two; the central and the peripheral nervous system. Neurons -​ These are the basic units of function and structure of the nervous system. -​ They carry information through the nervous system through nerve impulses. Types of Neurons: Sensory Neurons -​ It receives initial stimuli from the receptors. Transmits nerve signals to the spinal cord. Interneurons -​ They "read the impulses sent to by the neurons. -​ It determines what response should be generated. Motor Neurons -​ Transmit impulses from the brain to the effector cells. What is a reflex? -​ Reflex reactions happen without you having to think about them - they are involuntary.  -​ This is because the central nervous system sends electrical signals to the muscles before the brain can pick up the message. SENSORY NEURONS Carries information to spinal cord INTERNEURONS Passes the impulse to motor neuron MOTOR NEURONS Carries impulse to the muscles Behavior is the way in which a person acts in response to stimulus or situation. These response can aid survival. Stimulus: A thing or event that evokes a specific functional reaction in an organ or tissue. EXAMPLE If you hear a loud noise, The stimulus is the loud noise. Your response is your action. Humans respond to both internal and external stimuli External Internal An external stimulus is a change in the An internal stimulus is a change inside the envirónment around us. For example, the body. For example, the feeling of hunger. heat of an oven. EXAMPLES You feel cold, so you put on a jacket - EXTERNAL A dog feels the sun's heat, so it goes to lay in the shade. - EXTERNAL You have an infection, so you run a fever. - INTERNAL Autonomic nervous system -​ consists of nerves that connect the CNS (central nervous system) to the visceral organs such as the heart, stomach, and intestines. It meditates unconscious activities. Somatic nervous system -​ consists of nerves that go to the skin and muscles and is involved in conscious activities.  2.​ The Ovarian Cycle EGG PRODUCTION -​ All females are born with approximately two million egg cells in their lifetime. -​ By the time the female reaches puberty, it would go down to about 400,000. -​ Like the sperm cells, the egg cells also contain 23 chromosomes. -​ During puberty, the increased production of hormones enables one immature egg to complete its development each month. -​ The mature egg is what we call ova Ovaries -​ Where the egg is produced Uterus -​ where the ovum goes if no sperm is around to fertilize the egg Endometrium -​ the inner lining of the uterus that sheds during menstruation Progesterone -​ Sex hormone that signals the body to prepare for fertilization Ovulation -​ monthly release of an ovum from the ovary Follicles -​ cluster of cells that surrounds the immature egg  -​ If you do get pregnant, your body will produce human chorionic gonadotropin (hCG). This is the hormone pregnancy tests detect. -​ If you don't get pregnant, the corpus luteum will shrink away and be resorbed. -​ This leads to decreased levels of estrogen and progesterone. -​ The uterine lining will shed during your period. -​ You may experience symptoms of premenstrual syndrome PMS). PMS: -​ bloating -​ Breast swelling -​ Mood swings -​ Headache -​ Weight gain -​ Food cravings During menstruation Progesterone estrogen LSH ( luteinising FH (follicle hormone) stimulating hormone) low low low low During Luteal phase Progesterone estrogen LSH ( luteinising FH (follicle hormone) stimulating hormone) high low -​ The luteal phase starts after ovulation and ends on the first day of your period. During the Follicular Stage Progesterone Estrogen LSH FH low high high high During Ovulation Progesterone Estrogen LSH FH high high high Corpus Luteum  -​ term for yellow hormone-secreting body that secretes progesterone and estrogen that causes the uterine lining. Fallopian tube -​ site of fertilization II. Protein Synthesis 1.​ Identification of DNA as Genetic Material Genetics: -​ It is the branch of biology concerned with the study of heredity and variations. -​ Variation is the differences between individuals within a species. Identification of DNA as Genetic Material: INFORMATION It must contain the information necessary to make an entire organism TRANSMISSION It must be passed from parent to offspring. REPLICATION It must be copied. VARIATION It must be capable of changes. NUCLEIC ACID STRUCTURE -​ DNA and RNA are large macromolecules with several levels of complexity 1. Nucleotides form the repeating units is the basic building block of nucleic acids. 2. Nucleotides are linked to form a strand 3. Two strands can interact to form a double helix 4. The double helix folds, bends and interacts with proteins resulting in 3-D structures in the form-of chromosomes CHARGAFF'S RULE The rule that in DNA there is always equality in quantity between the bases A and T and between the bases G and C. One side: ATA TCA TGC GGG Other side: TAT AGT ACG CCC One side: A G T GAA CAT TA A Otherside: T C A CTT GTA ATT Difference between DNA and RNA RNA  -​ RNA is single-strand -​ RNA is not found in chromosomes because it does not carry the genetic code -​ RNA reads the DNA code and takes the information out of the nucleus. -​ RNA's main job is to build proteins! DNA -​ DNA is double strand -​ DNA cannot leave the nucleus. Messenger RNA -​ It carries complementary genetic code copied from DNA during transcription, in the form of triplets of nucleotides called codons. Ribosomal RNA (rRNAs) -​ combine with proteins and enzymes in the cytoplasm to form ribosomes, which act as the site of protein synthesis. Transfer RNA (tRNAs) -​ essential components of translation. Where their main function is the transfer of amino acids during protein synthesis Transcription - the transfer of genetic instructions in DNA to mRNA 1.​ RNA polymerase attaches to the promoter region of a gene on a strand of DNA. 2.​ DNA strands separate, exposing nucleotides ready for copying. 3.​ Messenger RNA (mRNA) pairs with a DNA template strand 4.​ Nucleotides are added until RNA polymerase reaches a termination sequence in the DNA and releases mRNA 5.​ mRNA moves out of the nucleus, the the nucleus pores, into cytoplasm. mRNA TAC TCG GGG CGC ATC CAA AUG AGC CCC GCG UAG GUU T-A A-U C-G G-C 6.​ A ribosome binds with a start codon in mRNA. The start codon is AUG 7.​ Transfer RNA (tRNA) has a complementary anticodon that attaches to a corresponding mRNA codon. tRNA carries an amino acid.  8.​ As the ribosome moves along the strand of mRNA more amino acids are added to the growing chain. 9.​ At the STOP codon, the ribosome releases the mRNA and an amino acid chain 10.​The amino acid chain folds into a three dimensional shape called a protein. STOP codons: UAG, UAA, and UGA. - these codons signal the end of the polypeptide chain during translation mRNA: AUG AGC CCC GCG UAG GUU tRNA: UAC UCH GGG CGC AUC CAA A-U C-G G-C U-A 2. Genetic Mutation MUTATION -​ Changes in the chromosome of an organism that is inheritable and are permanent. -​ Mutations can happen spontaneously or can be caused by mutagens or mutagenic agents. Types: 1.​ Chromosome number 2.​ Chromosome structure 3.​ Nucleotide sequence Based on Chromosome number -​ a change in chromosomes may be euploidy (whole genome) or an aneuploidy (change in the number of chromosomes) > Klinefelter syndrome > Turner syndrome > Down syndrome Aneuploidy is often caused by a phenomenon called “nondisjunction” or the inability of the homologous sex chromosomes to segregate during meiosis Down syndrome (Trisomy) -​ nondisjunction -​ Results in embryo with three copies of chromosome 21 instead of the usual 2 -​ Before or at conception a pair of 21st chromosomes in either the sperm or the egg fails to separate and is replicated in every cell of the body. -​ Can happen to both male and female Klinefelter Syndrom ( 47, XXY) -​ extra X Chromosome that is believed to be caused by a random error -​ This error usually occurs during meiosis -​ Individuals with klinefelter typically have small testes that produce a reduced amount of testosterone Turner syndrome (Congenital ovarian hypoplasia) -​ females typically have 2 X chromosome but individuals with turner syndrome only have 1. -​ One copy of the X chromosome is missing or altered. -​ Reducing functioning of the ovaries. -​ eggs usually die prematurely and most ovarian tissue breaks down before birth. Based on chromosome structure Deletion - loss of a segment Duplication - pair in excess Inversion - reversed from end to end Translocation - transfer of a chromosome part to a nonhomologous chromosome. Examples: Normal: THE CAT RAN FAR mutation: THE CAT CAT RAN FAR -​ duplication normal: THE CAT RAN FAR mutation: THE RAT CAN FAR -​ inversion normal: ABCDEFG mutation: ABCEFG  -​ deletion Chrom 1: ABCD Chrom 2: EFGH after: ABCH After: EFGD -​ translocation Based on nucleotide sequence > point mutation (microlesion) -​ deletion or insertion of one nucleotide pair > Frameshift mutation -​ the insertion or deletion of a number of nucleotides in the DNA sequence Point mutation (microlesion) -​ nonsense mutation: this results in the formation of a STOP codon due to substitution of a nitrogenous base -​ Missense mutation: results when one nitrogenous base is replaced and the result is an altered codon that does not form into a stop codon -​ Silent mutation - this result when one nitrogenous base is altered but the same amino acid is produced. Sickle cell anemia -​ point mutation occurs in the beta-hemoglobin gene. It converts a GAG codon(6th codon) into GUG codon which encodes the amino acid rather than glutamic acid. -​ Cannot carry oxygen as efficiently as normal round cells -​ Stiff and sticky making prone to clumping and blocking blood flow -​ Normal blood cells live about 120 days but sickle cells die within 10-20 days leading to anemia III. Evolution How the idea of evolution evolved: Charles Darwin Charles Darwin: -​ Darwin embarked from England on the beagle in Dec 1831. The primary mission of the voyage was to chart poorly known stretches of the South American coastline, leaving Darwin free to explore the continent and islands, including the Galápagos Islands. Observations -​ individuals in a population vary in their heritable characteristics. -​ Organisms produce more offspring that the environment can support Inferences  -​ individuals that are well suited to their environment tend to leave more offsprings than other individuals -​ Over time favorable traits accumulate the population He observed many examples of adaptations in The Origin of Species, Darwin proposed that evolution occurs by natural selection. Because resources are limited in nature, organisms with heritable traits that favor survival and reproduction will tend to leave more offspring than their peers, causing the traits to increase in frequency over generations. Theory of natural selection Natural selection is a process in which individuals with certain heritable traits survive and reproduce at a higher rate than the others because of those traits. Evidences of Evolution 1.​ Embryology -​ descent from a common ancestor, they started the same but just gradually evolved with different traits. 2.​ Homology -​ traits present in two or more organisms that were inherited from the common ancestor -​ Similar body parts but different uses. 3.​ Vestigial structures -​ structures of animals that are gradually disappearing -​ Lost their function through evolution; appendix 4.​ Genetics -​ same ancestors, same genetic code. 5.​ Fossils -​ evolutionary changes that occurred in various groups of organisms 6.​ Biogeography -​ the distribution of species on earth provides evidence that informs our understanding of both the evolution of life and the movement of continents