Comprehensive CAPS Life Sciences Study Notes

DNA - The Code of Life

  • There are two types of nucleic acids: DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid).
  • Location and roles:
    • DNA: located on chromosomes in the nucleus; forms the genes.
    • RNA: formed in the nucleus but functions mainly in the cytoplasm.
  • Structure of nucleic acids:
    • Nitrogenous bases come in two groups: purines (adenine A, guanine G) and pyrimidines (cytosine C, thymine T in DNA; cytosine C, uracil U in RNA).
    • Complementarity:
    • Cytosine pairs with guanine (C ≡ G).
    • Adenine pairs with thymine in DNA (A ≡ T); in RNA, adenine pairs with uracil (A ≡ U).
    • DNA base pairing is held together by weak hydrogen bonds; double helix model proposed by Watson & Crick (1953).
  • Nucleotides are the monomers of both DNA and RNA.
    • Each nucleotide consists of:
    • NB: nitrogenous base
    • S: sugar (deoxyribose in DNA; ribose in RNA)
    • P: phosphate
  • Location of DNA:
    • Nuclear DNA forms chromosomes within the nucleus; together with proteins, these form chromatin.
    • Extra-nuclear DNA found in chloroplasts (chloroplast DNA, ctDNA) and mitochondria (mitochondrial DNA, mtDNA).
  • DNA replication (before cell division): where identical copies of DNA are made.
    • Occurs during interphase (before mitosis and meiosis).
    • Process (summary):
    1. The double helix unwinds.
    2. Hydrogen bonds break; strands unzip.
    3. Each original strand serves as a template to form a new strand.
    4. Free nucleotides attach to the template by complementary base pairing (A↔T, C↔G).
    5. Two identical DNA molecules form, each composed of one original strand and one new strand.
    • Enzymes control replication.
  • RNA types and structure:
    • There are three main types of RNA:
    • Ribosomal RNA (rRNA): found in ribosomes in the cytoplasm.
    • Messenger RNA (mRNA): produced in the nucleus, exits to cytoplasm to be translated.
    • Transfer RNA (tRNA): found in cytoplasm; brings amino acids to ribosome.
    • RNA is typically single-stranded; sugar is ribose (not deoxyribose); thymine replaced by uracil (U).
  • Similarities & differences between DNA and RNA:
    • Similarities:
    • Both have sugar–phosphate backbones and nitrogenous bases.
    • Both participate in protein synthesis.
    • Differences:
    • DNA: double-stranded, uses deoxyribose, contains thymine; DNA’s location is nucleus/mitochondria/chloroplasts; DNA replication stores genetic information across generations.
    • RNA: single-stranded, uses ribose, contains uracil; functions in transcription and translation.
  • DNA replication (details you should know):
    • Before cell division, DNA replicates to ensure each daughter cell receives an identical set of chromosomes.
    • Conceptually the process creates two genetically identical DNA molecules, each with one original strand and one new strand.
  • Protein synthesis (central dogma overview):
    • Transcription: DNA → mRNA in the nucleus.
    • Translation: mRNA → protein in the cytoplasm at the ribosome; tRNA brings amino acids matching mRNA codons; amino acids linked by peptide bonds to form a protein.
    • Codons on mRNA are read in triplets; a codon specifies an amino acid; anticodons on tRNA pair with codons to deliver the correct amino acids.
  • DNA profiling (forensic genetics):
    • How it works: patterns of DNA fragments are visualized on a profile; a DNA profile is used to identify individuals by comparing with known DNA.
    • Uses include: diagnosing inherited disorders; criminal identification; establishing paternity; tracing siblings separated at birth; identifying remains.
    • Limitations/ethical issues:
    • Small DNA samples may not be unique to an individual.
    • Private labs may lack uniform testing standards/quality controls.
    • Human interpretation can introduce error.
    • Profiling can be expensive.
    • Potential for revealing sensitive information (e.g., HIV status) and face prejudice.
  • Key terms (glossary-style recap):
    • Nucleotide, Nucleic acid, Chromosome, Chromatin, Extra-nuclear DNA, Codon, Anticodon, Template, Replication, Transcription, Translation, DNA profile.
  • Quick connections to foundational principles:
    • Genetic information flow from DNA to RNA to protein underlies all cellular function.
    • Complementarity ensures accurate copying and expression of genes.
    • Mutations and DNA profiling underpin evolution, genetic disorders, forensic science, and medical diagnostics.

Meiosis

  • Meiosis overview:
    • Meiosis is the division of a germ cell into four haploid gametes, each with half the chromosome number of the parent.
    • Occurs during gametogenesis (gamete formation).
    • In many organisms meiosis occurs after fertilization in others (bread mould example).
  • Phases (Meiosis I and II):
    • Meiosis I (reduction division):
    • Interphase: DNA replication; chromosomes duplicate; each chromosome has two sister chromatids.
    • Prophase I: homologous chromosomes pair up (synapsis) forming bivalents; crossing-over occurs (exchange of genetic material).
    • Metaphase I: homologous pairs align randomly at the equator (random orientation).
    • Anaphase I: homologous chromosomes (each still double-stranded) are pulled to opposite poles; sister chromatids stay together.
    • Telophase I: two new nuclei form; cytoplasm divides to produce two haploid cells; chromosomes still double-stranded.
    • Meiosis II (equational division):
    • Prophase II: nuclear membrane dissolves; chromosomes condense.
    • Metaphase II: chromosomes align singly along the equator.
    • Anaphase II: sister chromatids are pulled apart to opposite poles.
    • Telophase II: four haploid cells form; each has half the original chromosome number; cells are genetically different.
  • Significance of meiosis:
    • Produces haploid gametes, maintaining chromosome number across generations after fertilization (diploid zygote formed by fertilization becomes diploid again).
    • Crossing over and Random arrangement of chromosomes during metaphase I & II introduce genetic variation, increasing genetic diversity in offspring.
  • Abnormal meiosis:
    • Non-disjunction can occur during Anaphase I or II, leading to aneuploidy or polyploidy.
    • Aneuploidy: gamete has an abnormal number of chromosomes.
    • Polyploidy: gamete has extra chromosome sets.
  • Examples discussed:
    • Down syndrome: trisomy 21 (47 chromosomes); often due to non-disjunction.
    • Karyotyping is used to detect abnormal chromosome numbers.
  • Terminology you should recall:
    • Homologous chromosomes, bivalent, chiasma, spindle fibers, centromere, diploid (2n), haploid (n).
  • Connections to real-world relevance:
    • Genetic variation from meiosis is a cornerstone of evolution and diversity.
    • Abnormal meiosis informs clinical genetics, prenatal screening, and diagnosis.

Reproduction in Vertebrates (Overview) / Human Reproduction

  • Reproduction strategies:
    • External fertilisation: fertilization occurs outside the female's body; water is required for transport and to prevent drying; many offspring produced to offset high mortality.
    • Internal fertilisation: fertilization occurs inside the female; common in terrestrial species; fewer offspring but higher survival rate.
  • Modes of development:
    • Ovipary: eggs laid outside body; development may be fertilized internally or after laying.
    • Ovovivipary: eggs fertilized internally but hatch inside the mother; young are relatively developed when born.
    • Vivipary: young develop inside the uterus with nutrients from the mother via placenta; live birth.
  • Amniotic egg and extra-embryonic membranes (in birds/reptiles):
    • Amnion: encloses amniotic cavity with amniotic fluid for cushioning.
    • Chorion: facilitates gas exchange.
    • Allantois: stores waste; participates in gas exchange.
    • Yolk sac: provides nutrition.
  • Precocial vs Altricial development (birds):
    • Precocial: hatchlings are relatively well-developed, eyes open, can move/feed themselves; examples include finches, canaries, crows, swallows, mynahs.
    • Altricial: hatchlings are helpless, eyes closed, need parental care; most passerines and many seabirds fall into this category.
    • About 60% of bird species are altricial.
  • Parental care: strategies include nest-building, guarding eggs, provisioning food, or internal gestation with placental nourishment (viviparity in mammals).
  • Amniotic egg vs mammalian pregnancy:
    • Amniotic eggs are common in reptiles and birds; eggs have shells that reduce dehydration; membranes (amniotic, chorion, allantois, yolk sac) support embryo.
    • In mammals, embryos are nourished via placenta; most mammals are viviparous.
  • Human reproductive anatomy (summary):
    • Male: testes (seminiferous tubules), sertoli cells (nurse developing sperm), Leydig cells (testosterone production), epididymis (sperm maturation and storage), vas deferens, seminal vesicles, prostate, Cowper’s glands; penis delivers sperm via urethra.
    • Female: ovaries (ova in follicles; estrogen & progesterone production), Fallopian tubes/oviducts (site of fertilization; carry ovum to uterus), uterus (endometrium thickening for implantation), cervix, vagina; urinary bladder; vulva.
  • Gametogenesis:
    • Spermatogenesis: occurs in testes; spermatogonia undergo meiosis to form four haploid sperm; several stages with Sertoli cells providing nutrition; SRY gene on Y chromosome influences development.
    • Oogenesis: occurs in ovaries; one mature ovum is produced from a follicle after meiosis; cytoplasm is unevenly divided; polar bodies form.
  • Menstrual cycle (ovarian and uterine cycles):
    • Ovarian cycle: development and release of a Graafian follicle; ovulation around day 14 of a ~28-day cycle; LH surges trigger ovulation; corpus luteum forms after ovulation and secretes progesterone.
    • Uterine cycle: endometrium thickens under estrogen and progesterone; if fertilization occurs, corpus luteum maintains pregnancy via progesterone; if not, corpus luteum degenerates; menstruation occurs (~day 28).
  • Hormones involved (simplified):
    • FSH (pituitary): stimulates follicle development; estrogen rise begins endometrial preparation.
    • LH (pituitary): triggers ovulation; forms corpus luteum; progesterone production to maintain pregnancy.
    • Estrogen: thickens endometrium; regulates many secondary sexual characteristics.
    • Progesterone: maintains endometrial lining and pregnancy; supports gestation.
    • Other relevant hormones/proteins: hCG (not always detailed in notes), testosterone in males, prolactin for milk production; oxytocin for childbirth (not deeply elaborated here).
  • Contraception (summary of options and mechanisms):
    • Barrier methods: condom, female condom, diaphragm, loop/IUD; prevent fertilization/implantation.
    • Hormonal methods: pill (oestrogen/progestin) inhibits ovulation; injections (progestin); implants (not detailed here).
    • Sterilisation: vasectomy (males) – blocks sperm transport; tubal ligation (females).
    • Other: withdrawal method; rhythm (calendar) method; effectiveness varies.
  • Fertilisation and implantation:
    • Sperm travel through uterus to Fallopian tube; fertilisation occurs when a sperm penetrates an ovum; zygote forms (2n, 46 chromosomes).
    • Zygote undergoes mitotic divisions to form blastocyst that implants into the endometrium.
    • Placenta forms from chorionic villi and uterine tissue; placenta functions include attachment, nutrient/ gas exchange, waste removal; umbilical cord connects embryo to placenta.
    • Amniotic fluid cushions the fetus; amnion surrounds the embryo.
  • Placental hormones and pregnancy maintenance:
    • Corpus luteum secretes progesterone to maintain pregnancy until placenta takes over.
    • Placenta eventually secretes hormones to maintain pregnancy (e.g., progesterone).
  • Contraception and public health implications:
    • Understanding contraception helps reduce unintended pregnancies; public health strategies include education and access to contraception.

HUMAN REPRODUCTION – Key structural and functional notes

  • Process flow (fertilization to implantation to birth):
    • Copulation introduces sperm into vagina; sperm travel up through uterus to Fallopian tubes.
    • Ovulation releases an ovum from Graafian follicle into Fallopian tube; if sperm fertilizes, zygote forms.
    • Zygote divides by mitosis to form a blastocyst; blastocyst implants into uterine endometrium; placenta forms; embryo develops into a fetus; gestation lasts ~9 months.
  • Gametogenesis in humans:
    • Spermatogenesis: produces millions of sperm; constant production throughout reproductive life in males.
    • Oogenesis: produces a single ovum per cycle; cytoplasmic division results in one mature ovum and polar bodies.
  • The menstrual and ovarian cycles interplay with hormones to regulate ovulation, endometrium preparation, and menstruation.
  • Embryo to fetus: development includes amniotic membranes, placenta, and umbilical cord; exposure to maternal physiology supports growth.

Genetics (Overview and Key Concepts)

  • Basic terminology:
    • Gene: a DNA segment at a locus that influences a characteristic.
    • Alleles: alternative forms of a gene; can be dominant or recessive.
    • Genotype: the genetic makeup (e.g., AA, Aa, aa).
    • Phenotype: observable trait (e.g., brown eyes).
    • Homozygous: two identical alleles (AA or aa).
    • Heterozygous: two different alleles (Aa).
    • Dominant allele: masks the recessive in a heterozygote.
    • Recessive allele: expressed only in homozygous form.
  • Modes of inheritance:
    • Complete (simple) dominance: one allele completely dominates the other; phenotype reflects dominant allele.
    • Incomplete dominance: heterozygote shows an intermediate phenotype (e.g., red x white = pink).
    • Codominance: both alleles contribute to phenotype (e.g., AB blood type).
    • Multiple alleles: more than two alleles exist for a gene (e.g., blood types IA, IB, i).
    • Sex-linked: genes located on sex chromosomes (X-linked phenotypes more common in males when recessive).
  • Pedigree analysis basics:
    • Used to track inheritance of traits, determine whether a trait is dominant/recessive, and assess carrier status.
  • Monohybrid cross: single trait cross; phenotypic ratio in F1 often 3:1 for complete dominance in the F2.
  • Dihybrid cross (two traits): expected phenotypic ratio 9:3:3:1 under complete dominance and independent assortment.
  • Blood typing and ABO system:
    • Alleles: I^A, I^B, i; I^A and I^B are co-dominant; i is recessive to both.
    • Genotypes and phenotypes:
    • Type A: IAIA or IAi
    • Type B: IBIB or IBi
    • Type AB: IAIB
    • Type O: ii
  • Mutations:
    • Gene mutations: point mutations (base substitution) and frameshift mutations (insertion/deletion).
    • Chromosomal mutations/aberrations: changes in chromosome structure or number; non-disjunction can cause Down syndrome (trisomy 21).
    • Effects of mutations can be harmful, neutral, or advantageous; some can be fixed in a population.
  • Genetic disorders mentioned (examples): Down syndrome (trisomy 21), Sickle cell anemia (point mutation on chromosome 11), Haemophilia, Albinism, color blindness (often X-linked).
  • Genetic technologies:
    • Genetic engineering: deliberate modification of organisms using biotechnology.
    • Cloning: producing genetically identical organisms.
    • Stem cells: potential to differentiate into various tissues; embryonic vs cord blood sources; ethical debates.
    • DNA profiling: forensic uses; advantages and limitations discussed earlier.
  • Tracing genetic lineage and pedigrees:
    • Pedigree diagrams indicate inheritance across generations; symbols show sex and phenotype status; used to infer carrier status and disease risk.

Nervous System and Sense Organs

  • Nervous system organization:
    • Central nervous system (CNS): brain and spinal cord.
    • Peripheral nervous system (PNS): nerves outside CNS; subdivided into the somatic and autonomic systems.
  • Neurons and nerve impulses:
    • Three neuron types:
    • Sensory neurons: carry impulses from receptors to CNS.
    • Motor neurons: carry impulses from CNS to effector organs (muscles, glands).
    • Interneurons (connector neurons): carry impulses within CNS.
    • Neuron structure: dendrites, cell body, nucleus, axon; myelin sheath and neurilemma insulate to speed transmission; impulse travels from dendrites → cell body → axon; synapse (gap) where neurotransmitters cross to next neuron.
  • Reflex actions and reflex arc:
    • Reflex action: rapid, automatic response to a stimulus.
    • Reflex arc components: receptor → sensory neuron → interneuron → motor neuron → effector.
    • Example described: knee-jerk reflex; reflex provides quick protective response.
  • Sense organs and receptors:
    • Eye: structure includes sclera, choroid, retina; cornea, iris, pupil, lens, ciliary body; aqueous and vitreous humours; macula (high cone density); blind spot.
    • Ear: outer ear (pinna, ear canal), middle ear (tympanic membrane, ossicles: hammer, anvil, stirrup; Eustachian tube), inner ear (cochlea with organ of Corti; semicircular canals for balance).
    • Receptors: light, sound, taste, smell, temperature, pressure, pain, balance, etc.
  • Visual system: accommodation and pupil reflexes (pupillary mechanism).
  • Common neurological disorders and injuries:
    • Alzheimer’s disease; Multiple sclerosis; injuries to brain/spinal cord; effects on memory, balance, and autonomic control.
  • Drugs and the nervous system:
    • Drugs can stimulate or inhibit neurotransmitter action; effects include memory changes, paranoia, anxiety.

Endocrine System and Homeostasis

  • Endocrine system basics:
    • Glands: endocrine glands secrete hormones into the bloodstream; exocrine glands have ducts.
    • Major glands and hormones (examples):
    • Hypothalamus: ADH (vasopressin), regulates pituitary activity.
    • Pituitary (hypophysis): TSH, FSH, LH, prolactin, growth hormone.
    • Thyroid: thyroxine (T4) – regulates metabolic rate.
    • Pancreas: insulin and glucagon – regulate blood glucose.
    • Adrenal glands: adrenaline (epinephrine), aldosterone – stress response and salt balance.
    • Ovaries: estrogen, progesterone – female development and pregnancy maintenance.
    • Testes: testosterone – male development.
  • Negative feedback and homeostasis:
    • Homeostasis: maintenance of a relatively constant internal environment.
    • Negative feedback: a change in a controlled condition triggers a response that counteracts the initial change to restore normal levels (e.g., thyroxine and TSH levels).
  • Hormone regulation examples:
    • Thyroid axis: low thyroxine → pituitary releases more TSH → thyroid release increases thyroxine; high thyroxine → less TSH → thyroxine production decreases.
    • Glucose regulation: high blood glucose → pancreas secretes insulin → lowers glucose; low glucose → glucagon from pancreas raises glucose by converting glycogen to glucose.
    • Stress response: adrenaline prepares body for emergency (increases heart rate, blood flow to muscles, dilates bronchi, etc.).
  • Diabetes mellitus:
    • Type 1: pancreas stops producing insulin; requires insulin injections.
    • Type 2: insulin produced but not effectively used; managed via diet, exercise, sometimes medication.
  • Hormone vs nervous coordination:
    • Hormones are chemical messengers; slower but longer-lasting; act on many targets; can interact.
    • Nerves transmit electrical impulses rapidly; specific to particular effectors; fast responses.
  • Negative feedback examples in practice:
    • ADH controls water re-absorption in kidneys; aldosterone controls Na+ reabsorption; hypothalamus/pituitary regulate many axes.

Homeostasis

  • Core idea: maintain stable internal conditions despite environmental changes.
  • Osmoregulation and water balance:
    • Nephron and ADH regulate water re-absorption; hypothalamus senses osmolality; pituitary secretes ADH accordingly.
    • Water balance adjustments result in dilute or concentrated urine depending on needs.
  • Thermoregulation:
    • Heat loss/gain regulated by vasodilation/vasoconstriction; sweating; hypothalamus acts as thermostat.
  • Gas exchange and metabolism:
    • Carbon dioxide and oxygen balance tightly regulated by respiratory and circulatory adjustments.

Plant Responses to the Environment

  • Plant hormones (growth substances):
    • Auxins (IAA): promote tropisms (phototropism and geotropism), promote cell elongation, apical dominance, root development.
    • Gibberellins: promote internode elongation, root growth, flowering, leaf aging, stomatal closure during drought.
    • Abscisic acid (ABA): dormancy in seeds, dormancy in apical buds, inhibits growth; involved in drought responses.
  • Tropisms:
    • Phototropism: growth toward light; stems are positively phototropic; roots are negatively phototropic.
    • Geotropism: growth in response to gravity; roots are positively geotropic; stems are negatively geotropic.
    • Auxin distribution controls bending by stimulating differential growth on sides of plant organs.
  • Phototropism mechanism:
    • Auxin produced at shoot tips moves downward; uneven distribution causes bending toward light due to differential growth.
  • Geotropism mechanism:
    • Auxins accumulate on the lower side of horizontally placed roots; differential growth causes downward bending.
  • Weed control using plant hormones:
    • Hormone-based herbicides rely on auxin analogs to kill targeted weeds while sparing crops.
  • Plant defense mechanisms:
    • Thorns, chemical secretions, and leaf/fruit defenses protect plants from herbivores and pathogens.

Evolution by Natural Selection

  • Evidence for evolution:
    • Fossils (paleontology): dating fossils via relative dating and radiometric dating; fossils reveal gradual changes and transitional forms; phylogenetic trees illustrate relationships.
    • Homologous structures: similar anatomical plans across species imply common ancestry and adaptive modification.
    • Biogeography: related species cluster geographically; similar environments in different regions host different species.
    • Molecular biology and genetics: DNA/protein sequence similarities reflect descent and relatedness.
  • Sources of variation:
    • Mutations: random changes in DNA sequences; can be point mutations or frameshifts; can be neutral, harmful, or advantageous.
    • Meiosis: crossing over and independent assortment generate novel genetic combinations; random fertilisation adds to variation.
  • Lamarck vs Darwin:
    • Lamarckism: inheritance of acquired characteristics; traits modified by use/disuse are passed to offspring.
    • Darwinism: variation arises randomly; natural selection favors advantageous traits; populations accumulate beneficial traits over generations.
  • Speciation and evolution:
    • Allopatric speciation occurs when geographic barriers separate populations; independent evolution leads to new species.
    • Punctuated equilibrium proposes long periods of little change interrupted by rapid evolutionary bursts.
  • Human impact on evolution:
    • Artificial selection (selective breeding) demonstrates how humans influence trait frequencies.

Human Evolution

  • Out of Africa hypothesis:
    • Modern humans (Homo sapiens) originated in Africa and migrated to other continents; mitochondrial DNA (mtDNA) studies support a common maternal ancestor in Africa.
  • Key fossil evidence and timeline:
    • Ardipithecus ramidus (5-4 mya), Australopithecus afarensis (3.9-2.9 mya), Australopithecus africanus (2-2 mya), Homo habilis (~2.2-1.6 mya), Homo erectus (1.5-0.2 mya), Homo sapiens (~200k years ago to present).
  • Evolutionary trends observed in fossil record:
    • Increase in brain size over time.
    • Foramen magnum moved forward indicating bipedalism.
    • Reduction in prognathism and dental size (teeth) as diet shifts toward cooked food.
    • Brow ridges reduce; cranium becomes more rounded; facial structure becomes flatter.
    • Pelvis becomes shorter and wider; spine more curved to support upright walking.
  • Phylogenetic relationships:
    • Transitional fossils (e.g., Australopithecus sediba) show mosaic traits bridging earlier and later Homo species.
  • Modern human origins:
    • Mitochondrial DNA and genetic evidence indicate a recent common maternal ancestor (mitochondrial Eve) in Africa.
  • Comparative anatomy with African apes:
    • Humans differ in cranium size, foramen magnum position, brow ridges, spine curvature, pelvis shape, dentition, and jaw projection.

Human Impact on the Environment

  • Climate change & greenhouse effect:
    • Greenhouse gases (CO2, methane CH4, water vapour) trap heat and keep Earth warm; excessive greenhouse gas intensities lead to enhanced greenhouse effect and global warming.
    • Primary causes: burning fossil fuels, deforestation, agriculture (methane from ruminants, rice paddies, waste decomposition).
    • Consequences: increased evaporation, more intense rainfall and flooding, sea-level rise, droughts, more wildfires, biodiversity loss.
  • Carbon footprint:
    • A measure of total greenhouse gas emissions by individuals, populations, or organizations per year.
  • Ozone layer and CFCs:
    • Ozone layer absorbs UV radiation; destruction by CFCs threatens skin cancer risk and eye damage; strategies include phasing out CFCs and protecting ozone.
  • Deforestation & biodiversity loss:
    • Removal of forests reduces carbon sequestration, disrupts habitats, and reduces biodiversity.
  • Water quality and availability:
    • Dams affect water storage; wetlands purify water; pollution from agriculture and industry degrades water bodies; eutrophication from excess nutrients; heavy metals from mining.
  • Waste management:
    • Solid waste disposal requires safe landfill design to prevent leachate; recycling reduces energy use and pollution; methane can be captured for energy.
  • Food security and GMOs:
    • Genetically modified organisms (GMOs) can increase yield, resist pests/drought, improve shelf-life, and alter nutritional content; debates include ethics, safety, and ecological impacts.
  • Sustainable practices:
    • Reduce/reuse/recycle; switch to renewable energy; protect biodiversity; adopt sustainable farming and land management.

Ethical, Philosophical & Practical Implications

  • Genetic engineering and cloning:
    • Potential benefits: medical proteins, disease resistance, increased yields.
    • Ethical concerns: effects on ecosystem, animal welfare,