Science Reviewer (3rd Quarter) PDF

SCIENCE REVIEWER (3rd Quarter) Nervous System -​ Increases heart rate, dilates pupils, Function: The nervous system controls and and redirects blood flow to muscles, communicates information throughout the enhancing physical perfor...

SCIENCE REVIEWER (3rd Quarter) Nervous System -​ Increases heart rate, dilates pupils, Function: The nervous system controls and and redirects blood flow to muscles, communicates information throughout the enhancing physical performance. body, allowing for coordination of bodily functions and responses to internal and Parasympathetic Nervous System: external stimuli. -​ Promotes "rest and digest" Components: functions, calming the body after stress. -​ Slows heart rate, enhances digestion, and conserves energy. Neurons: Basic units of the nervous system that transmit signals. Structure: Dendrites: -​ Branch-like structures that receive signals from other neurons and transmit them to the cell body. 1.​ Central Nervous System (CNS) -​ Comprises the brain and spinal cord. Cell Body (Soma): -​ Responsible for processing sensory -​ Contains the nucleus and information, regulating bodily organelles; processes incoming functions, and enabling cognitive signals and integrates information. abilities such as thinking, memory, and emotion. Axon: -​ A long, thin projection that transmits 2.​ Peripheral Nervous System (PNS) electrical impulses away from the -​ Connects the CNS to limbs and cell body to other neurons or organs. muscles. Divided into: Myelin Sheath: Somatic Nervous System -​ A fatty layer that surrounds the axon, -​ Controls voluntary movements and insulating it and speeding up the transmits sensory information to the transmission of impulses. CNS. -​ Involves motor neurons that Axon Terminals: stimulate skeletal muscles. -​ The endpoints of the axon that release neurotransmitters to Autonomic Nervous System communicate with other neurons or -​ Regulates involuntary bodily target cells. functions, such as heart rate, digestion, and respiratory rate. Further divided into: Endocrine System Function: The endocrine system secretes and releases hormones to regulate various Sympathetic Nervous System: body functions, including metabolism, -​ Prepares the body for "fight or flight" growth, and reproduction. responses during stressful situations. SCIENCE REVIEWER (3rd Quarter) -​ Manage stress response and metabolism; produce hormones like cortisol (stress hormone) and adrenaline (epinephrine). Ovaries: -​ Produce eggs and female hormones (estrogen and progesterone) that regulate the menstrual cycle and support pregnancy. Testes: -​ Produce sperm and male hormone (testosterone) that influences male characteristics and reproductive functions. Pituitary Gland: -​ Known as the master gland; controls other glands and stimulates growth. Hormones: Chemical messengers -​ Divided into anterior and posterior influencing growth, metabolism, and lobes, each producing different reproduction. hormones. -​ Extra male hormones are produced in testes and female hormones in Thyroid Gland: ovaries. -​ Regulates metabolism, energy -​ Some hormones have short-term production, and brain development. effects while others have long-term -​ Produces thyroid hormones (T3 and influences (e.g., growth, changes at T4) that influence metabolic rate and the onset of puberty). energy levels. -​ Hormonal changes happen during Parathyroid Gland: puberty; sudden mood swings are -​ Controls calcium levels in the blood, relatively caused by increasing essential for bone health and muscle number of hormones in the body at function. this stage. -​ Produces parathyroid hormone -​ Common Symptoms: Hormonal (PTH) that increases blood calcium imbalances occur when there is too levels. much or too little of a hormone in the blood, leading to various health Thymus Gland: issues. -​ Facilitates maturation of T-cells for the immune system, playing a Reproductive System crucial role in immune response. Function: The reproductive system is responsible for procreation and production Pancreas: of gametes (sperm in males and eggs in -​ Regulates blood sugar levels by females). producing insulin (lowers blood sugar) and glucagon (raises blood 1.​ Male Reproductive System: sugar). -​ Plays a key role in metabolism and energy balance. Adrenal Glands: SCIENCE REVIEWER (3rd Quarter) Testes: -​ Produce sperm and testosterone, the primary male sex hormone. Ovaries: -​ -​ Produce eggs and female hormones Epididymis: (estrogen and progesterone). -​ Stores and matures sperm, allowing them to gain motility. Fallopian Tubes: -​ -​ Site of fertilization; transport the ova Vas Deferens: from the ovaries to the uterus. -​ Transports sperm from the epididymis to the ejaculatory duct. Uterus: -​ Nurtures the fertilized egg and Seminal Vesicles: supports fetal development. -​ Produce a fluid that nourishes sperm and constitutes a significant portion Cervix: of semen. -​ Connects the uterus to the vagina; allows passage of sperm and Prostate Gland: menstrual fluid. -​ Produces a fluid that helps protect and energize sperm, contributing to Vagina: semen. -​ Receives sperm and serves as the birth canal during childbirth. Bulbourethral Glands: -​ Produce a pre-ejaculatory fluid that Hormones in the Reproductive System lubricates the urethra and neutralizes acidity. Estrogen: -​ Source: Primarily produced in the Urethra: ovaries, but also in smaller amounts -​ Carries urine from the bladder and by the adrenal glands and fat semen from the reproductive system tissues. out of the body. -​ Functions: Regulates the menstrual cycle and development of female Penis: secondary sexual characteristics. -​ Delivers sperm to the female reproductive system during sexual Progesterone: intercourse. -​ Source: Produced mainly by the ovaries after ovulation, and by the 2.​ Female Reproductive System: placenta during pregnancy. -​ Functions: Prepares the uterus for pregnancy and regulates the menstrual cycle. SCIENCE REVIEWER (3rd Quarter) -​ The lining of the uterus sheds Testosterone: through the vagina. -​ Source: Primarily produced in the -​ Most people bleed for three to five testes in males, with smaller days, but a period lasting only three amounts produced in the ovaries days to as many as seven days is and adrenal glands in females. usually not a cause for worry. -​ Functions: Influences male characteristics and sperm Follicular Phase: production. -​ Begins on the day of the period and ends at ovulation; overlaps with the Luteinizing Hormone (LH): menstrual phase. -​ Source: Secreted by the anterior -​ The level of the hormone estrogen pituitary gland. rises, causing the lining of the uterus -​ Functions: Triggers ovulation and (the endometrium) to grow and stimulates testosterone production. thicken. -​ Follicle-stimulating hormone (FSH) Follicle-Stimulating Hormone (FSH): causes follicles in the ovaries to -​ Source: Also secreted by the grow. anterior pituitary gland. -​ During days 10 to 14, one of the -​ Functions: Stimulates development developing follicles will form a fully of ovarian follicles and controls mature egg (ovum). ovum production. Ovulation: Feedback Mechanisms -​ Occurs roughly at about day 14 in a 28-day menstrual cycle. ​ Positive Feedback: -​ A sudden increase in another -​ Occurs when the product of a hormone—luteinizing hormone reaction leads to an increase in that (LH)—causes the ovary to release reaction (e.g., oxytocin release its egg. during childbirth) Luteal Phase: ​ Negative Feedback: -​ Lasts from about day 15 to day 28. -​ Occurs when the product of a -​ Egg leaves the ovary and begins to reaction leads to a decrease in that travel through the fallopian tubes to reaction, stabilizing the system (e.g., the uterus. hormone regulation in the menstrual -​ The level of the hormone cycle). progesterone rises to help prepare the uterine lining for pregnancy. Menstrual Cycle -​ If the egg becomes fertilized by -​ Occurs every month starting at ages sperm and attaches itself to the 10-13. uterine wall (implantation), -​ Lasts approximately 28 days. pregnancy occurs. -​ Divided into two cycles: ovarian -​ If pregnancy doesn’t occur, estrogen cycle and uterine cycle. and progesterone levels drop, and the thick lining of the uterus sheds Phases of the Menstrual Cycle: during the period. Menstrual Phase: -​ -​ Also called menstrual period or -​ menses; begins on the first day of the period. SCIENCE REVIEWER (3rd Quarter) contractions, creating a cycle that intensifies until the baby is born. Protein Synthesis Overview Protein synthesis is the biological process through which cells generate new proteins. It involves two main stages: transcription and translation. Additionally, DNA replication is the process by which a cell duplicates its DNA before cell division. Both processes are essential for cellular function and reproduction. Maintaining Homeostasis 1.​ Homeostasis: -​ This is the state of balance within the body, where various systems work together to maintain stable internal conditions, such as temperature, pH, and glucose levels. 2.​ Negative Feedback: -​ This mechanism counteracts changes to return the body to its set point. For example: -​ In hot environments, the body cools down by sweating and dilating blood vessels. -​ In cold environments, the body generates heat through shivering and constricts blood vessels to conserve warmth. -​ Blood glucose regulation is another 1.​ Transcription example, where insulin lowers blood -​ Location: Occurs in the nucleus of sugar levels when they are too high, eukaryotic cells. and glucagon raises them when they Process: are too low. -​ Initiation: 3.​ Positive Feedback: -​ The enzyme “RNA polymerase” -​ This mechanism amplifies changes binds to a specific region of the DNA rather than counteracting them. A called the promoter, which marks the classic example is childbirth: beginning of a gene. -​ Pressure on the cervix triggers uterine contractions, which release -​ DNA Unwinding: hormones that cause more SCIENCE REVIEWER (3rd Quarter) -​ The DNA double helix unwinds, -​ The initiator tRNA carrying exposing the bases of the gene to methionine binds to the start codon. be transcribed. -​ Elongation: -​ RNA Synthesis: -​ The ribosome reads the mRNA in -​ RNA polymerase reads the DNA sets of three bases (codons). template strand and synthesizes a -​ Each codon corresponds to a complementary strand of messenger specific amino acid. RNA (mRNA). -​ Transfer RNA (tRNA) molecules bring the appropriate amino acids to -​ Base Pairing: the ribosome. -​ Adenine (A) pairs with Uracil (U) in -​ Each tRNA has an anticodon that is RNA (instead of Thymine (T) in complementary to the mRNA codon. DNA). -​ For example, if the mRNA codon is -​ Cytosine (C) pairs with Guanine (G). AGU, the tRNA with the anticodon UAC will bring the amino acid serine. -​ Termination: -​ The ribosome facilitates the -​ RNA polymerase continues to formation of peptide bonds between elongate the mRNA strand until it adjacent amino acids, creating a reaches a termination signal in the growing polypeptide chain. DNA. -​ The mRNA strand is then released, -​ Termination: and the DNA strands rejoin. -​ The process continues until the ribosome encounters a stop codon -​ Post-Transcriptional (UAA, UAG, or UGA) on the mRNA. Modifications (in eukaryotes): -​ The completed polypeptide chain is -​ The mRNA undergoes processing, released from the ribosome. which includes: -​ The ribosome disassembles, and the -​ Capping: Addition of a 5' cap to the mRNA can be translated again or mRNA for protection and degraded. recognition. -​ Polyadenylation: Addition of a poly-A tail to the 3' end to enhance stability. -​ Splicing: Removal of non-coding regions (introns) and joining of coding regions (exons) to form a mature mRNA. 2.​ Translation -​ Location: Occurs in the cytoplasm at the ribosome. Process: -​ Initiation: -​ The mature mRNA binds to the small subunit of the ribosome. -​ The ribosome scans the mRNA for the start codon (AUG), which codes for the amino acid methionine. SCIENCE REVIEWER (3rd Quarter) Mutations reading frame and thus all of the codons Definition of Mutation: Change in DNA that follow it. base pair sequence due to environmental -​ As this example shows, a frameshift factors or errors during DNA replication. mutation can dramatically change -​ Can lead to changes in proteins how the codons in mRNA are read. translated by the DNA. This can have a drastic effect on the protein product. Point Mutations A point mutation is a change in a single nucleotide in DNA. This type of mutation is usually less serious than a chromosomal alteration. An example of a point mutation is a mutation that changes the codon UUU to the codon UCU. -​ Point mutations can be silent, missense, or nonsense mutations. The effects of point mutations depend on how they change the genetic code. Silent: Mutated codon codes for the same amino acid. CAA (glutamine) → CAG (glutamine) Evidences of Evolution 1.​ Fossil Evidence Missense: Mutated codon codes for a -​ Definition: Fossils are the different amino acid. preserved remains or traces of CAA (glutamine) → CCA (proline) organisms from the past, typically found in sedimentary rock. Nonsense: Mutated codon is a premature stop codon. -​ Types of Fossils: CAA (glutamine) → UAA (stop) -​ Body Fossils: Actual remains of organisms, such as bones, teeth, Frameshift Mutations and shells. A frameshift mutation is a deletion or insertion of one or more nucleotides that -​ Trace Fossils: Indirect evidence of changes the reading frame of the base life, such as footprints, burrows, and sequence. Deletions (remove nucleotides), coprolites (fossilized feces). and Insertions (add nucleotides). Consider the following sequence of bases in RNA: -​ Importance: -​ Fossils provide a historical record of ex. AUG-AAU-ACG-GCU = life on Earth, showing how species start-asparagine-threonine-alanine have changed over time. Now, assume an insertion occurs in this -​ Transitional fossils illustrate gradual sequence. Let’s say an A nucleotide is changes in species, such as inserted after the start codon AUG: “Archaeopteryx”, which shows ex. AUG-AAA-UAC-GGC-U = features of both dinosaurs and start-lysine-tyrosine-glycine modern birds. -​ The fossil record demonstrates Even though the rest of the sequence is patterns of extinction and unchanged, this insertion changes the SCIENCE REVIEWER (3rd Quarter) diversification, supporting the idea of and nucleic acids indicate common common descent. ancestry. -​ Phylogenetics: Scientists use 2.​ Comparative Anatomy molecular data to construct -​ Definition: Comparative anatomy phylogenetic trees, illustrating involves studying the similarities and evolutionary relationships based on differences in the structures of genetic similarities and differences. different organisms. -​ Importance: -​ Types of Structures: -​ Molecular evidence provides a -​ Homologous Structures: Body precise understanding of parts that share a common ancestry evolutionary relationships. but may have different functions -​ It allows scientists to trace the (e.g., forelimbs of humans, whales, evolutionary history of species and and bats). understand the mechanisms of evolution at the genetic level. -​ Analogous Structures: Body parts that serve similar functions but do 4.​ Comparative Embryology not share a common ancestry (e.g., -​ Definition: Comparative embryology wings of insects and birds). is the study of the similarities and differences in the embryonic -​ Vestigial Structures: Body parts development of different organisms. that have lost their original function through evolution (e.g., the human -​ Key Points: appendix). -​ Early embryonic stages of many vertebrates (e.g., fish, birds, -​ Importance: mammals) exhibit striking -​ Homologous structures support the similarities, such as the presence of idea of common descent, indicating pharyngeal pouches and tails. that different species evolved from a -​ These similarities suggest that these shared ancestor. species share a common ancestor -​ Comparative anatomy helps and that certain developmental scientists understand evolutionary pathways are conserved across relationships and the adaptive different lineages. significance of various traits. -​ As development progresses, the embryos diverge and develop into 3.​ Molecular Evidence distinct forms, reflecting their -​ Definition: Molecular evidence evolutionary adaptations. involves comparing the DNA, RNA, and protein sequences of different -​ Importance: organisms to determine evolutionary -​ Comparative embryology provides relationships. evidence for common descent, as it shows that different species can -​ Key Points: have similar developmental -​ Genetic Similarity: Closely related processes. species have more similar genetic -​ It highlights the evolutionary material (e.g., humans and relationships among species and the chimpanzees share about 98% of mechanisms of development that their DNA). have been preserved through -​ Molecular Homology: Similarities in evolution. the molecular structure of proteins