CBSE Class 12 Biology Exercise Solutions

How to Use This Page

1. Read each NCERT chapter thoroughly — Biology requires precise terminology and conceptual understanding. 2. Attempt all textbook exercises and back-of-chapter questions on your own before checking solutions. 3. Pay special attention to labelled diagrams — they carry marks and clarify your answers. 4. Use scientific terminology — examiners look for specific keywords like "syngamy," "recombinant DNA," "apomixis," etc. 5. Practise writing answers within word limits: short answers 40-60 words, long answers 120-150 words. 6. Revise using the exam checklist at the end.

Key Concepts (Quick Recap)

Unit 1: Reproduction

• Reproduction in Organisms — Types (sexual, asexual); lifespan; phases of life; vegetative propagation; binary fission, budding, fragmentation, spore formation.
• Sexual Reproduction in Flowering Plants — Flower structure; pollination (self, cross); double fertilisation; embryo sac; post-pollination events; seed and fruit formation; apomixis; polyembryony.
• Human Reproduction — Male and female reproductive systems; spermatogenesis; oogenesis; menstrual cycle; fertilisation; implantation; placenta; embryonic development; parturition; lactation.
• Reproductive Health — Contraceptive methods; MTP; STDs; infertility; IVF, ZIFT, GIFT; amniocentesis; population stabilisation.

Unit 2: Genetics and Evolution

• Heredity and Variation — Mendel's laws; monohybrid and dihybrid crosses; incomplete dominance; codominance; multiple alleles; polygenic inheritance; pleiotropy; sex determination; mutations; pedigree analysis.
• Molecular Basis of Inheritance — DNA as genetic material; DNA replication; transcription; translation; genetic code; regulation of gene expression (lac operon); Human Genome Project; DNA fingerprinting.
• Evolution — Origin of life; evolution of life forms; evidences (paleontological, morphological, anatomical, embryological, biochemical); Darwin's natural selection; Lamarckism; Hardy-Weinberg principle; adaptive radiation; convergent evolution; brief account of human evolution.

Unit 3: Biotechnology

• Biotechnology: Principles and Processes — Recombinant DNA technology; restriction enzymes; gel electrophoresis; PCR; vectors (plasmids, bacteriophages); host organisms; selectable markers; transformation; bioreactors; downstream processing.
• Biotechnology and Its Applications — Genetically modified organisms (GMOs); Bt cotton; Golden rice; Gene therapy; Molecular diagnosis (PCR, ELISA); transgenic animals; ethical issues; biopiracy.

Unit 4: Ecology

• Organisms and Populations — Habitat; niche; adaptations; population attributes (density, natality, mortality, sex ratio, age distribution); population growth curves; population interactions (mutualism, competition, predation, parasitism, commensalism, amensalism).
• Ecosystem — Structure (biotic, abiotic); productivity; decomposition; energy flow; ecological pyramids; nutrient cycling (carbon, phosphorus); succession.
• Biodiversity and Conservation — Levels of biodiversity (genetic, species, ecological); patterns; importance; loss of biodiversity; causes; biodiversity hotspots; IUCN categories; in situ conservation (protected areas, biosphere reserves); ex situ conservation (zoos, cryopreservation, seed banks).
• Environmental Issues — Pollution (air, water, soil); greenhouse effect and global warming; ozone depletion; deforestation; eutrophication; solid waste management; biological magnification.

I. Choose the Best Answer (MCQs)

1. Which of the following is a vegetative propagule?

• (a) Seed
• (b) Spore
• (c) Runner
• (d) Pollen grain

2. Double fertilisation in angiosperms involves:

• (a) Fusion of two male gametes with two eggs
• (b) Fusion of one male gamete with the egg and the other with the polar nuclei
• (c) Fusion of one male gamete with the synergid and the other with the antipodal
• (d) Fusion of one male gamete with the polar nuclei only

3. The secretory phase of the menstrual cycle is also called:

• (a) Proliferative phase
• (b) Luteal phase
• (c) Follicular phase
• (d) Menstrual phase

4. Which of the following is an example of codominance?

• (a) Flower colour in snapdragon
• (b) ABO blood groups
• (c) Seed shape in pea
• (d) Tt genotype producing tall plants

5. The lac operon is repressed when:

• (a) Lactose is present and glucose is absent
• (b) Lactose is absent
• (c) Glucose is present and lactose is absent
• (d) Both lactose and glucose are present

6. PCR (Polymerase Chain Reaction) is used for:

• (a) Cutting DNA at specific sites
• (b) Amplifying DNA segments
• (c) Joining DNA fragments
• (d) Separating DNA fragments by size

7. Which of the following is an example of mutualism?

• (a) Cattle egret and cattle
• (b) Orchid growing on a mango tree
• (c) Lichens (fungus + alga)
• (d) Lion and deer

8. The upright pyramid of numbers is found in:

• (a) A parasitic food chain
• (b) A grassland ecosystem
• (c) A single tree ecosystem
• (d) A forest ecosystem with few large trees

9. Bt cotton is resistant to:

• (a) Fungi
• (b) Bacteria
• (c) Insects (specifically lepidopteran pests)
• (d) Viruses

10. Which of the following is an ex situ conservation method?

• (a) Biosphere reserve
• (b) National park
• (c) Seed bank
• (d) Wildlife sanctuary

II. Fill in the Blanks

1. The process of formation of gametes is called gametogenesis.

2. In double fertilisation, the fusion of the male gamete with the two polar nuclei forms the primary endosperm nucleus (3n).

3. The implantation of the blastocyst occurs in the uterus (endometrium).

4. The testis is located outside the abdominal cavity in the scrotum, which provides a temperature 2-2.5 degrees Celsius lower than body temperature.

5. The exchange of genetic material between non-sister chromatids of homologous chromosomes is called crossing over.

6. The enzyme that joins DNA fragments is called DNA ligase.

7. In the lac operon, lactose acts as an inducer by binding to the repressor protein and inactivating it.

8. The process of amplifying DNA using PCR involves three steps: denaturation, annealing, and extension.

9. The ecological pyramid that is always upright for biomass in a forest ecosystem is the pyramid of biomass.

10. The IUCN category for species that are at high risk of extinction in the wild is Endangered.

III. True or False

1. Asexual reproduction produces genetically identical offspring.

True. Asexual reproduction involves only one parent and does not involve the fusion of gametes or meiosis. The offspring are produced by mitosis and are genetically identical to the parent (clones), barring mutations.

2. In a dicot embryo, the embryonal axis has the radicle at the lower end and the plumule at the upper end.

True. The embryonal axis of a dicot embryo has the radicle (future root) at the lower end and the plumule (future shoot) at the upper end, with the cotyledons on either side.

3. Spermatogenesis results in the formation of one sperm cell from each primary spermatocyte.

False. Each primary spermatocyte undergoes meiosis I to form two secondary spermatocytes, and each secondary spermatocyte undergoes meiosis II to form two spermatids. Thus, one primary spermatocyte produces four sperm cells.

4. A heterozygous individual (Aa) will show the recessive phenotype.

False. In complete dominance, a heterozygous individual (Aa) shows the dominant phenotype because the dominant allele (A) masks the expression of the recessive allele (a). The recessive phenotype appears only in the homozygous condition (aa).

5. DNA replication is conservative, meaning the parent strand remains intact and a completely new strand is synthesised.

False. DNA replication is semi-conservative — each new DNA molecule consists of one parent strand and one newly synthesised strand. This was demonstrated by Meselson and Stahl's experiment using N-15 and N-14.

6. Restriction enzymes cut DNA at random positions.

False. Restriction enzymes (restriction endonucleases) recognise specific DNA sequences (recognition sites) and cut the DNA at or near these sites. For example, EcoRI recognises GAATTC and cuts between G and A.

7. In a food chain, energy increases at each trophic level.

False. Energy decreases at each trophic level. Only about 10% of energy is transferred from one trophic level to the next (10% law). The rest is lost as heat, used for metabolism, or remains in undecayed matter.

8. Biodiversity is higher in the polar regions than in the tropics.

False. Biodiversity is highest in the tropics (particularly in tropical rain forests) and decreases towards the poles. The tropics have more stable climates, more solar energy, and longer evolutionary history, supporting greater species diversity.

IV. Match the Following

V. Answer Briefly

Q1. Differentiate between asexual and sexual reproduction.

Asexual reproduction involves a single parent, no gamete formation, no fusion of gametes, and produces genetically identical offspring (clones). It is a rapid process (binary fission, budding, fragmentation, spore formation). Sexual reproduction involves two parents, formation and fusion of gametes, and produces genetically diverse offspring due to recombination. It is a slower process but provides variation that helps in adaptation and evolution.

Q2. What is double fertilisation? Why is it called "double"?

Double fertilisation is the process unique to angiosperms where both male gametes from the pollen tube participate in fusion — one male gamete fuses with the egg cell to form the diploid zygote (syngamy), and the other male gamete fuses with the two polar nuclei to form the triploid primary endosperm nucleus (triple fusion). It is called "double" because two fertilisation events occur simultaneously — syngamy and triple fusion — making it a distinctive feature of flowering plants.

Q3. What are the main differences between spermatogenesis and oogenesis?

Spermatogenesis occurs in the testes, starts at puberty, produces four functional sperm from each primary spermatocyte, and continues throughout life. Oogenesis occurs in the ovaries, starts during fetal development (but completes only at fertilisation), produces one functional ovum and two/three polar bodies from each primary oocyte, and has long arrest phases (at prophase I until puberty, at metaphase II until fertilisation). Spermatogenesis is continuous; oogenesis is cyclic and discontinuous.

Q4. State Mendel's Law of Independent Assortment.

Mendel's Law of Independent Assortment states that when two or more pairs of traits are inherited together, the alleles of different gene pairs assort independently of one another during gamete formation. In other words, the distribution of alleles of one trait does not affect the distribution of alleles of another trait. This law applies only when genes are on different chromosomes or are far apart on the same chromosome (no linkage).

Q5. What is DNA fingerprinting? What is its principle?

DNA fingerprinting is a technique used to identify individuals based on their unique DNA patterns. The principle is that every individual (except identical twins) has unique repetitive DNA sequences (satellite DNA) that vary in number and location. These Variable Number Tandem Repeats (VNTRs) produce a unique pattern when DNA is cut with restriction enzymes, separated by gel electrophoresis, and visualised as bands. This pattern is as unique as a fingerprint and is used in forensic science, paternity disputes, and identification.

Q6. Differentiate between in situ and ex situ conservation.

In situ conservation means protecting species in their natural habitats — through national parks, wildlife sanctuaries, biosphere reserves, and protected forests. It allows species to live and evolve in their natural environment. Ex situ conservation means protecting species outside their natural habitats — through zoos, botanical gardens, seed banks, cryopreservation, and tissue culture. It is used for species that cannot survive in the wild or whose habitat is destroyed.

Q7. What are the major causes of biodiversity loss?

The major causes (often called the "evil quartet") are: (1) Habitat loss and fragmentation — destruction of forests, grasslands, and wetlands for agriculture, urbanisation, and development. (2) Over-exploitation — excessive harvesting of species for food, medicine, and trade. (3) Alien species invasion — introduced species that outcompete native species (e.g., water hyacinth, Parthenium). (4) Co-extinction — when one species goes extinct, species dependent on it also face extinction.

Q8. What is the significance of the Human Genome Project?

The Human Genome Project (HGP) was an international effort to sequence the entire human genome. Its significance includes: (1) It identified approximately 20,000-25,000 genes in human DNA. (2) It determined the sequences of the 3 billion base pairs in the human genome. (3) It helps understand genetic diseases and develop targeted therapies. (4) It provides data for evolutionary studies by comparing human DNA with other species. (5) It enables personalised medicine and pharmacogenomics.

VI. Answer in Detail

Q1. Describe the process of double fertilisation in angiosperms. What is its significance?

Double fertilisation is a unique feature of angiosperms (flowering plants) involving two simultaneous fertilisation events. The process begins when a pollen grain lands on the stigma and germinates, producing a pollen tube that grows through the style and enters the ovule through the micropyle. The pollen tube carries two male gametes. Inside the ovule, the pollen tube enters one of the synergids and releases the two male gametes. The first male gamete fuses with the egg cell to form the diploid zygote (2n) — this is called syngamy. The second male gamete fuses with the two polar nuclei (present in the central cell of the embryo sac) to form the triploid primary endosperm nucleus (3n) — this is called triple fusion. Together, syngamy and triple fusion constitute double fertilisation. After fertilisation, the zygote develops into the embryo, and the primary endosperm nucleus develops into the endosperm, which provides nourishment to the developing embryo. The ovule develops into the seed, and the ovary develops into the fruit. Significance of double fertilisation: 1. It ensures that the endosperm develops only when fertilisation occurs, preventing wasteful nutrient investment in unfertilised ovules. 2. The triploid endosperm provides nutrition to the developing embryo, increasing the chances of seedling survival. 3. It is an evolutionary advancement that makes angiosperms more efficient in resource utilisation compared to gymnosperms, where endosperm is pre-formed (haploid) and not a result of fertilisation. 4. Double fertilisation ensures that the energy stored in the endosperm is used only for a viable embryo, making the reproductive process more economical.

Q2. Explain the molecular basis of inheritance — from DNA replication to protein synthesis.

The Central Dogma describes the flow of genetic information: DNA → RNA → Protein. This involves three key processes: 1. DNA Replication (DNA → DNA): DNA replication is semi-conservative — each new DNA molecule has one parent strand and one newly synthesised strand. The process involves: (a) Initiation: The enzyme helicase unwinds the double helix at the origin of replication. (b) Elongation: DNA polymerase III adds nucleotides to the 3' end of the growing strand, synthesising the leading strand continuously and the lagging strand in Okazaki fragments. RNA primase synthesises short RNA primers that DNA polymerase extends. (c) Termination: DNA ligase joins the Okazaki fragments, and primers are replaced with DNA. The Meselson-Stahl experiment (1958) using N-15 and N-14 confirmed semi-conservative replication. 2. Transcription (DNA → RNA): Transcription is the process of synthesising RNA from a DNA template. It occurs in three steps: (a) Initiation: RNA polymerase binds to the promoter region of the DNA. In bacteria, the sigma factor helps recognise the promoter. (b) Elongation: RNA polymerase moves along the DNA template strand (3'→5') and synthesises RNA in the 5'→3' direction using ribonucleotides. Only one strand (the template strand) is transcribed; the other is the coding strand. (c) Termination: In bacteria, the rho factor terminates transcription. In eukaryotes, the primary transcript undergoes processing — capping (5' methyl guanosine cap), splicing (removal of introns), and polyadenylation (poly-A tail at 3' end) — to form mature mRNA. 3. Translation (RNA → Protein): Translation occurs at the ribosome and involves: (a) Initiation: The small ribosomal subunit binds to mRNA at the start codon (AUG). The initiator tRNA carrying methionine binds to the start codon. The large ribosomal subunit then joins, forming the initiation complex. (b) Elongation: The ribosome has three sites — A (aminoacyl), P (peptidyl), and E (exit). A new aminoacyl-tRNA enters the A site. A peptide bond forms between the amino acids at the A and P sites. The ribosome translocates, moving the tRNA from A to P and releasing the empty tRNA from the E site. This cycle repeats. (c) Termination: When a stop codon (UAA, UAG, UGA) enters the A site, release factors bind, causing the polypeptide chain to be released and the ribosome to dissociate. The genetic code is the set of rules by which nucleotide triplets (codons) specify amino acids. Key features: it is universal (same codons in almost all organisms), degenerate (multiple codons for one amino acid), non-overlapping, and comma-less. This entire process — from DNA to functional protein — constitutes the molecular basis of inheritance, ensuring that genetic information is accurately transmitted and expressed.

Q3. Explain the steps involved in recombinant DNA technology (genetic engineering).

Recombinant DNA technology involves cutting and joining DNA fragments from different sources and introducing them into a host organism to produce desired products. The key steps are: 1. Isolation of the Gene of Interest (Foreign DNA): The desired gene is identified and isolated from the donor organism. This can be done by: (a) cutting the DNA with restriction enzymes (restriction endonucleases) that recognise specific sequences; (b) synthesising the gene chemically; or (c) using PCR to amplify the specific DNA fragment. The gene must also include regulatory sequences (promoter, terminator) for proper expression. 2. Insertion of the Gene into a Vector: A vector is a DNA molecule that can carry the foreign gene into a host cell. Common vectors include plasmids (pBR322, pUC19), bacteriophages, cosmids, and BACs. The vector is cut with the same restriction enzyme used to cut the gene, creating complementary sticky ends. The foreign gene is then inserted into the vector using DNA ligase, which forms phosphodiester bonds between the gene and the vector. This creates recombinant DNA (rDNA). 3. Introduction of rDNA into the Host Cell (Transformation): The recombinant vector is introduced into the host organism (usually E. coli) through: (a) heat shock method — mixing cells with rDNA and briefly heating to 42 degrees Celsius; (b) microinjection — directly injecting rDNA into the nucleus; (c) gene gun/biolistic method — bombarding cells with gold-coated DNA particles; (d) electroporation — using electrical pulses to create temporary pores in the cell membrane. 4. Selection of Transformed Cells (Selectable Markers): Not all host cells take up the recombinant DNA. Selectable markers (antibiotic resistance genes like ampicillin resistance or tetracycline resistance) help identify transformed cells. Only cells that have taken up the vector with the selectable marker can grow on antibiotic-containing media. Further screening (blue-white selection using lacZ gene) identifies cells with the recombinant vector versus empty vector. 5. Expression of the Gene and Product Recovery: The transformed host cells are cultured in bioreactors under optimal conditions. The gene of interest is expressed, and the product (protein) is produced. Downstream processing involves separating and purifying the product through filtration, chromatography, and other techniques to obtain the final product in usable form. Applications: Recombinant DNA technology has produced human insulin (Humulin), growth hormone, vaccines (Hepatitis B), Bt cotton, Golden Rice, and has applications in gene therapy, molecular diagnosis, and environmental management.

Q4. Describe the structure and function of the ecosystem. Explain energy flow and nutrient cycling.

Ecosystem Structure: An ecosystem consists of biotic (living) and abiotic (non-living) components. Abiotic components include sunlight, temperature, water, soil, minerals, and gases. Biotic components are organised into: (a) Producers (autotrophs): Green plants, algae, and cyanobacteria that convert solar energy into chemical energy through photosynthesis. (b) Consumers (heterotrophs): Primary consumers (herbivores) eat producers; secondary consumers eat primary consumers; tertiary consumers eat secondary consumers. (c) Decomposers: Bacteria and fungi that break down dead organic matter and recycle nutrients. Ecosystem Function: The two main functions of an ecosystem are energy flow and nutrient cycling. Energy Flow: Energy enters the ecosystem through producers (photosynthesis) and flows through the food chain. Key features: (a) Unidirectional: Energy flows from sun → producers → consumers → decomposers. It does not cycle back. (b) Lindeman's 10% law: Only about 10% of energy is transferred from one trophic level to the next. The rest is lost as heat (respiration), used for metabolism, or remains in undecayed matter. (c) GPP and NPP: Gross Primary Productivity (GPP) is the total energy captured by producers through photosynthesis. Net Primary Productivity (NPP) = GPP minus the energy used by producers for respiration (R). NPP is the energy available to herbivores. (d) Food chains and webs: A food chain shows linear energy transfer (grass → deer → lion). A food web shows interconnected food chains, providing stability to the ecosystem. (e) Ecological pyramids: Energy pyramid is always upright (energy decreases at each trophic level). Pyramid of numbers can be upright (grassland) or inverted (parasitic chain). Pyramid of biomass is upright in terrestrial ecosystems but inverted in aquatic ecosystems. Nutrient Cycling (Biogeochemical Cycles): Unlike energy, nutrients cycle between living and non-living components. Two important cycles: Carbon Cycle: Carbon enters the ecosystem through photosynthesis (CO2 → organic carbon). It returns to the atmosphere through respiration, decomposition, and combustion. Carbon is also stored in oceans (as dissolved CO2), fossil fuels (coal, petroleum), and as carbonates in rocks. Human activities (burning fossil fuels, deforestation) have disrupted the carbon cycle, increasing atmospheric CO2 and causing global warming. Phosphorus Cycle: Phosphorus cycles through rocks, soil, water, and organisms. It is released from rocks by weathering, absorbed by plants, passed through the food chain, and returned to soil through decomposition and excretion. Unlike carbon, phosphorus does not have a gaseous phase in its cycle. Phosphorus cycling is very slow. Human activities (phosphate mining, fertiliser runoff) cause eutrophication in water bodies. The key difference between energy flow and nutrient cycling is that energy flows in one direction (and is lost as heat at each step), while nutrients cycle continuously between organisms and the environment.

Q5. Discuss the different types of population interactions with examples. How do they affect population dynamics?

Organisms in an ecosystem interact with each other in various ways, and these interactions significantly affect population dynamics. The major types are: 1. Mutualism (+/+): Both species benefit from the interaction. Examples: Lichens (fungus provides shelter; alga provides food through photosynthesis); Rhizobium bacteria in root nodules of legumes (bacteria fix nitrogen for the plant; plant provides carbohydrates to bacteria); Fig and fig wasp (wasp pollinates the fig; fig provides oviposition site and food for wasp larvae). Mutualism increases the population of both species. 2. Competition (-/-): Both species are harmed as they compete for the same limited resource. Examples: Flamingos and fish competing for zooplankton in South American lakes; weeds competing with crop plants for nutrients, water, and light. According to Gause's Competitive Exclusion Principle, two closely related species competing for the same resources cannot coexist indefinitely — the competitively superior species will eventually exclude the other. Competition can lead to resource partitioning, where species evolve to use different resources or the same resource at different times. 3. Predation (+/-): The predator kills and eats the prey. The predator benefits; the prey is harmed. Examples: Tiger and deer; snake and frog; cat and rat. Predation plays an important role in maintaining species diversity by keeping prey populations in check and preventing competitive exclusion. Predators also help regulate community structure — the removal of a top predator can cause cascading effects (trophic cascade). 4. Parasitism (+/-): The parasite benefits at the expense of the host, but does not kill the host immediately. Examples: Cuscuta (dodder) is a parasitic plant that derives nutrition from the host plant; ticks on dogs; lice on humans; Plasmodium (malaria parasite) in humans. Parasites have evolved adaptations like hooks, suckers, and loss of digestive systems. Parasitism weakens the host, reducing its reproductive success and survival. 5. Commensalism (+/0): One species benefits; the other is unaffected. Examples: Cattle egret and cattle (egret catches insects disturbed by cattle; cattle are unaffected); orchid growing on a mango tree (orchid gets sunlight and support; mango tree is unaffected); barnacles on a whale. 6. Amensalism (-/0): One species is harmed; the other is unaffected. Examples: Penicillium fungus producing penicillin that kills bacteria (the fungus is unaffected by the bacteria); large trees shading small plants below (trees are unaffected; small plants are harmed by reduced light). These interactions regulate population sizes, maintain community structure, drive evolutionary adaptations (co-evolution), and contribute to biodiversity. For example, predator-prey dynamics create population cycles, and competitive exclusion can drive species diversification through niche differentiation.

Common Mistakes to Avoid

1. Confusing mitosis and meiosis in gametogenesis — Spermatogenesis and oogenesis involve meiosis, not mitosis. Primary spermatocyte/oocyte undergoes meiosis I and II. Be precise about which division produces what.

2. Mixing up codominance and incomplete dominance — Codominance = both alleles expressed equally (AB blood group). Incomplete dominance = intermediate phenotype (red + white = pink in snapdragon). These are different inheritance patterns.

3. Writing vague answers about DNA replication — Always mention the key enzymes: helicase (unwinding), primase (RNA primer), DNA polymerase III (elongation), DNA polymerase I (primer removal), and DNA ligase (joining fragments). Use scientific terms precisely.

4. Confusing in situ and ex situ conservation — In situ = in the natural habitat (national parks, biosphere reserves). Ex situ = outside natural habitat (zoos, seed banks, cryopreservation). Never mix these up.

5. Forgetting to draw and label diagrams — Biology board exams award marks for labelled diagrams. Always draw: reproductive systems, DNA structure, cell division stages, ecological pyramids, biotechnology processes, etc.

6. Writing incomplete answers for ecological pyramids — Always specify which type of pyramid (numbers, biomass, energy) and which ecosystem (grassland, forest, aquatic). Not all pyramids are upright — the pyramid of biomass in an aquatic ecosystem is inverted.

Exam Checklist

• [ ] I can describe all types of asexual and sexual reproduction with examples
• [ ] I can explain double fertilisation, embryo sac structure, and post-pollination events
• [ ] I can describe the male and female reproductive systems with labelled diagrams
• [ ] I can explain the menstrual cycle phases and hormonal regulation
• [ ] I can solve Mendelian crosses (monohybrid, dihybrid) with proper notation and ratios
• [ ] I can explain DNA replication (semi-conservative, Meselson-Stahl) and transcription/translation
• [ ] I can describe the lac operon and gene regulation
• [ ] I can explain the steps of recombinant DNA technology with correct terminology
• [ ] I can list and explain all types of population interactions with examples
• [ ] I can describe energy flow (10% law, GPP, NPP) and nutrient cycles (carbon, phosphorus)
• [ ] I can explain biodiversity levels, causes of loss, and conservation strategies
• [ ] I can draw and label key diagrams: reproductive systems, DNA structure, cell division, ecological pyramids