- D3 ✏︎ Organisms -
D3.1 - Human & Animal Reproduction (SL/HL)
LECTURE VIDEO
DESCRIPTION
Sex isn’t just about making more of you. It’s about shuffling the deck, mixing the genes, and creating a whole new human with zero instructions and a lot of screaming. Reproduction isn’t just biology. It’s a casino, a construction project, and a monthly hormonal meltdown all rolled into one.
This video gets uncomfortably intimate with the facts of life:
- Sexual vs. Asexual: Asexual reproduction is just cloning yourself with extra steps. Efficient, boring, genetically identical. Sexual reproduction? Two parents, half the DNA each, infinite combinations. It’s slower, riskier, and uses way more energy. But it gives evolution something to work with. Also, it’s more fun.
- The Plumbing: His & Hers – The male system is a mass-production factory—testicles churn out millions of sperm daily, epididymis handles quality control, and the penis is just the delivery truck. The female system is a curated archive—ovaries release one egg per month, fallopian tubes host the meet-cute, and the uterus is a five-star gestation suite complete with a self-cleaning function. Same goal. Very different logistics.
- Sperm & Egg: The Kamikaze and The Fortress – Sperm is a streamlined torpedo—DNA-packed head, mitochondria midpiece screaming “FASTER,” and a frantic tail. No cytoplasm, no repairs, no backup plan. The egg is a nutrient-packed giant surrounded by protective layers. Doesn’t move. Just waits. Thousands of sperm perish against its walls. One breaches. That’s not romance. That’s siege warfare.
- The Menstrual Cycle: 28 Days of Hormonal Warfare – FSH whispers “grow an egg,” estrogen builds a cozy uterine lining, then LH scream-spikes to yeet the egg out of the ovary. Progesterone maintains the penthouse suite until either fertilization happens or the lining sheds into a week of blood, cramps, and misery. Then repeat. For decades.
- Fertilization: The Swim of a Lifetime – Hundreds of millions start. A few hundred survive the journey. One penetrates the outer layers, triggers the cortical reaction, and slams the door behind it. No other sperm allowed. You began as a single cell that was very, very exclusive.
- IVF: When Nature Needs a Lab Coat – Egg retrieval. Sperm wash. Petri dish meet-cute. Embryo transfer. No fallopian tubes required. Science took romance and replaced it with a micropipette. Still works, though.
- Meiosis & Variation: Why You’re Not Your Sibling – Crossing over swaps chromosome chunks. Independent assortment shuffles the maternal/paternal deck. Random fertilization means any sperm meets any egg. The number of possible genetic combinations is higher than the number of atoms in the universe. You are statistically impossible. Congratulations.
Understand why sex exists, how your plumbing works, and why you are the winner of a 300-million-sperm race that you don’t even remember entering.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline of this video
00:01:16 – Sexual V.S. Asexual Reproduction
00:13:16 – Types Of Asexual Reproduction
00:21:31 – Sexual Reproduction Overview
00:24:20 – Male Reproductive Organs [Front view]
00:33:11 – Male Reproductive Organs [Side view]
00:35:46 – Female Reproductive Organs [Front view]
00:40:32 – Female Reproductive Organs [Side view]
00:42:38 – Sperm V.S Egg
00:49:03 – The Menstrual Cycle
01:10:33 – The Menstrual Cycle Curve
01:16:37 – Contraceptive pills
01:17:39 – Fertilisation (Natural)
01:23:30 – In Vitro Fertilisation (IVF)
01:30:15 – Meiosis & Variation
01:35:26 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.1 - Plant Reproduction (SL/HL)
LECTURE VIDEO
DESCRIPTION
Step aside, human dating apps—flowers have been running the “look at me, I’m pretty and full of nectar” game for 140 million years. Plant reproduction isn’t just about growing seeds; it’s a full production involving bribes, wind gambling, and seeds that refuse to wake up until conditions are perfect.
This video gets botanically suggestive with the birds, the bees, and the self-pollinating introverts:
- Flower Structure: The Architectural Bribe – Petals = flashy billboard. Stamens = the male squad (anthers produce pollen, filaments hold them up). Carpel = the female suite (stigma catches pollen, style is the hallway, ovary holds ovules). Every part has one goal: get that pollen transferred.
- Pollination: The Pollen Delivery Service – Wind gamblers release millions of lightweight grains and hope. Advertisers use nectar bribes, UV landing strips, and bee-friendly colours. Insect gets dusted, visits another flower, accidental matchmaking. Self-pollinators just skip the hassle. Introvert energy.
- Fertilization: The Double Date – Pollen tube grows down the style. One sperm fertilizes the egg → embryo. One sperm fertilizes polar nuclei → endosperm (snack supply). Two fertilizations, one pollen grain. Plants flexing.
- Seed Structure: The Survival Kit – Seed coat = armor. Embryo = the baby. Cotyledons = first leaves or food storage. Endosperm = lunchbox. Everything needed to travel through time and space.
- Seed Dispersal: Leaving the Nest – Wind seeds grow helicopter blades or parachutes. Animal seeds hitchhike on fur or get eaten, tour a digestive system, and exit fertilized. Explosive seeds literally yeet themselves. Plants don’t move, but their babies are global travelers.
- Germination: Waking Up Is Hard – Water rehydrates. Enzymes wake up. Radicle emerges first (root), then plumule (shoot). Seed coat splits. New plant commits to life. Or waits. Some seeds wait decades. Dormancy isn’t laziness. It’s strategy.
Understand why flowers are passive-aggressive matchmakers, how pollen grows a microscopic elevator, and why some seeds refuse to wake up until you’ve already given up and planted something else.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline Of This Video
00:01:11 – The BIG PICTURE
00:07:38 – The Flower Structure
00:17:44 – Pollination
00:23:43 – Fertilisation & Seed Production
00:36:22 – Promoting Cross Pollination
00:40:20 – Chemical Self-Incompatibility
00:44:42 – Fruit Formation
00:47:32 – Seed Dispersal
00:50:34 – Germination
01:01:50 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.1 - Human & Animal Reproduction (HL)
LECTURE VIDEO
DESCRIPTION
Your existence didn’t start at birth. It started with a hormonal disaster called puberty, one very determined sperm, and your mother pushing a watermelon through a keyhole. This is your origin story. It’s chaotic.
This video follows the messiest renovation project your body ever undertook:
- Puberty: Your Body’s Weird Glow-Up – Your brain suddenly sends out hormonal memos. Pituitary blasts FSH and LH like it’s announcing a rave. Voices crack. Hair appears. Everyone pretends this is normal. It is. Still embarrassing.
- Spermatogenesis vs. Oogenesis: Mass Production vs. Limited Edition – Males produce millions of sperm daily, lifetime supply. Females? All her eggs were made before she was born. One per month. The sperm factory never closes. The egg vault slowly empties. Biology said “equal rights? nah.”
- Preventing Polyspermy: No Entry After One – One sperm makes it through. Cortical granules rush out. The zona pellucida hardens into a biological “CLOSED” sign. This isn’t a party. It’s monogamous molecular commitment.
- Embryo Development: From Blob to Baby-Shaped – Cells divide. Morula. Blastocyst. Implantation. Three layers become your organs. Limbs sprout. Your tail disappears. You looked like a shrimp, then a lizard, then a tiny human. It was a journey.
- Pregnancy & The Placenta: The VIP All-Inclusive Resort – The placenta is half mother, half fetus, and 100% in charge. Hormones, oxygen, nutrients, waste removal. Umbilical cord is the lifeline. Amniotic fluid is the heated pool. Nine months of rent-free luxury. Then you get evicted.
- Birth: The Grand Eviction – Oxytocin starts contractions. More contractions = more oxytocin = more contractions. Cervix goes from “absolutely not” to “okay, fine.” Water breaks. Pushing. Crowning. Delivery. Baby is furious. Everyone cries. Welcome to Earth.
- Hormone Replacement Therapy: When the Ovaries Clock Out – Menopause arrives. Estrogen quits. Hot flashes. Mood swings. HRT tops up what the ovaries stopped producing. Not turning back time. Just making the transition less sweaty.
Understand how you went from a microscopic swimmer to a full human, why your mom deserves flowers, and what happens when your body’s hormone factory permanently shuts down.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Overview Of This Video
00:00:41 – Puberty
00:07:22 – Spermatogenesis [Structures Involved]
00:16:06 – Spermatogenesis Explained
00:26:04 – Spermatogenesis (Summary Page)
00:29:55 – The Nucleus during spermatogenesis
00:33:59 – Light Microscope Of Seminiferous Tubules
00:36:54 – Oogenesis [Structures Involved]
00:38:37 – Oogenesis Explained
00:52:37 – Oogenesis (Summary Page)
00:55:01 – Spermatogenesis V.S Oogenesis Summary
00:57:23 – Preventing Polyspermy
01:01:52 – Embryo Development
01:07:11 – Pregnancy Test
01:19:11 – The Placenta [Structure]
01:23:49 – The Placenta [Function]
01:35:44 – Labor & Birth
01:39:30 – Hormone Replacement Therapy (HRT)
01:43:45 – Question & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.2 - Inheritance (SL/HL)
LECTURE VIDEO
DESCRIPTION
Ever wonder why your brother got the height and you got the allergies? Blame Gregor Mendel and his horny pea plants. Inheritance is a genetic lottery where dominant genes act like celebrities, recessive ones lurk for generations, and sex-linked disorders have a “males only” dress code.
This video decodes the genetic gambling that made you who you are:
- Gregor Mendel: The Original Plant Shipper –This monk spent years getting peas pregnant and counting wrinkles. He discovered some genes are bullies (dominant) and some are introverts (recessive). Thanks, Mendel. Biology now involves peas.
- Key Concepts: Genotype = the script. Phenotype = what everyone sees. Homozygous = both alleles agree. Heterozygous = toxic situationship. Alleles = different versions of the same gene.
- Autosomal Dominant: One faulty copy and congrats, you’ve got it. Huntington’s, achondroplasia. Doesn’t skip generations. Loud. Proud. Inescapable.
- Autosomal Recessive: Needs two copies. You can be a carrier your whole life and never know. Then you meet another carrier and suddenly it’s 1 in 4. Cystic fibrosis, sickle cell. The genes that ghost for generations then show up uninvited.
- Sex-Linked Disorders: Mostly camping out on the X chromosome. Males have one X—if it’s faulty, they’re stuck with it. Females have a spare. This is why colorblindness and hemophilia are basically the “boys only” club no one wanted to join. Girls carry it. Boys inherit the drama.
- Codominance vs. Incomplete Dominance: Codominance says “both showing.” Blood type AB—A and B waving together. Incomplete dominance says “let’s compromise.” Red + white = pink. Very diplomatic.
- Pedigree Charts: Your family tree but with more shading and less awkward Thanksgivings. Squares = guys. Circles = gals. Shaded = affected. Half-shaded = carrier but don’t worry about it. Follow the pattern. Is it dominant? Recessive? Sex-linked? The chart knows all. It judges nothing. (It judges everything.)
- The Minor Stuff (Still Testable): Continuous variation = spectrum (height). Discontinuous = either/or (blood type). Phenotypic plasticity = same genes, different environment. SNPs = DNA typos that make cilantro taste like soap. Box and whisker plots = graphing where most people fall and which outlier needs attention.
Understand why you’re a walking combination of dominant bullies, recessive skeletons, and a few thousand genetic typos that somehow assembled into a functional human. You’re not perfect. You’re just statistically probable.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline Of This Video
00:00:32 – Inheritance, Genetics & Environment
00:05:28 – Karyogram, Autosomes, Sex chromosomes
00:11:45 – Gene, Allele, Locus
00:20:12 – Genotype & Phenotype
00:23:02 – The 5 Types Of Inheritance Patterns
00:23:33 – Autosomal Dominant Inheritance
00:33:18 – Test Cross
00:37:44 – Autosomal Recessive Inheritance (E.g., PKU)
00:46:20 – Sex Linked Inheritance (E.g., Haemophilia)
01:00:18 – Questions & Answers #1
01:02:59 – Incomplete Dominance (E.g., Hair Shape)
01:06:58 – Co-dominance (E.g., ABO Blood groups)
01:13:43 – Intro To Pedigrees
01:16:57 – Different Types Of Pedigrees Explained
01:30:53 – Who Is Gregor Mendel?
01:36:53 – Single Nucleotide Polymorphism (SNPS)
01:38:15 – Phenotypic Plasticity
01:40:28 – Continuous V.S Discontinuos Variation
01:43:27 – Box & Whisker Plot
01:48:05 – Questions & Answers #2
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.2 - Inheritance (HL)
LECTURE VIDEO
DESCRIPTION
Monohybrid crosses are cute. Dihybrid crosses are where things get messy—especially when genes are linked and refuse to follow Mendel’s rules like they’re going through a phase.
This video makes Punnett squares slightly less painful:
- Monohybrid Cross: One trait. Four boxes. 3:1 if both parents are heterozygous. You’ve done this since grade school. Moving on.
- Dihybrid Cross (Unlinked): Two traits. Sixteen boxes. 9:3:3:1 if the genes are independent and life is fair. Spoiler: life isn’t fair.
- Linked Genes: Genes on the same chromosome are basically in a committed relationship. They travel together. That 9:3:3:1 ratio? Gone. Parental combos dominate. Mendel is rolling in his grave.
- Recombinants: Crossing over during meiosis swaps DNA between chromosomes. New combos appear. The rebel children who don’t look like either parent. Frequency tells you how far apart genes are. More crossovers = further apart. Genetics has road trip energy.
- Chi-Squared Test: You predicted a ratio. Your actual counts don’t match. Is it significant or did you just get unlucky? Chi-squared does the math so you don’t have to argue. Low number? Accept your fate. High number? Something’s wrong. Linked genes. Bad data. Or you can’t count. Embarrassing.
Understand why some genes refuse to separate, how crossing over creates the weird kids, and when to trust the math over your gut.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline Of This Video
00:00:39 – Some Basics
00:10:39 – Monohybrid Cross
00:12:34 – Dihybrid Cross Intro
00:14:09 – Linked Genes [Dihybrid Cross]
00:23:24 – Question #1 [Linked Genes]
00:28:53 – Question #2 [Linked Genes]
00:31:14 – Recombinants In Linked Genes
00:37:05 – Unlinked Genes [Dihybrid Cross]
00:41:46 – Question #3 [Unlinked Genes]
00:44:39 – Question #4 [Unlinked Genes]
00:46:51 – Unlinked Genes On Same Chromosome
00:53:14 – Chi-Squared Test [Coin Toss example]
01:03:48 – Chi-Squared Test [Mendel Peas example]
01:09:46 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.3 - Homeostasis (SL/HL)
LECTURE VIDEO
DESCRIPTION
Your body hates change. Too hot? Sweat. Too cold? Shiver. Too much sugar? Insulin to the rescue. Too little? Glucagon brings the snacks. It’s a 24/7 balancing act involving hormones, organs, and the world’s most dramatic thermostat.
This video explores how your body obsesses over keeping things exactly the same:
- What Is Homeostasis?: Your body’s desperate attempt to keep everything stable while you do stupid stuff like eat three donuts or jump into cold water. It’s not relaxing. It’s working overtime. Constant internal nagging.
- Blood Glucose Regulation: The Sugar Tightrope: Eat carbs? Glucose spikes. Pancreas releases insulin. Liver stores the excess. Skip lunch? Glucose drops. Pancreas releases glucagon. Liver dumps sugar back in. It’s a hormonal see-saw and your pancreas is the annoying friend making sure it stays level.
- Diabetes: When the System Breaks: Type 1? Pancreas stopped making insulin. Autoimmune betrayal. Type 2? Cells stopped listening to insulin. Receptor fatigue from too many carbs. Either way, blood sugar goes rogue and now there’s finger pricks involved. Not ideal.
- Body Temperature Regulation: Your Internal Thermostat: Too hot? Blood vessels dilate. Heat radiates. Sweat glands activate. You become a salty, dripping mess. Too cold? Blood vessels constrict. Heat stays in. Muscles shiver to generate warmth. You become a shaky, miserable mess. Either way, you’re complaining.
- Endothermic vs. Ectothermic: Endotherms (you) generate internal heat. Expensive but worth it. Ectotherms (lizards) sunbathe like it’s a vacation. Cheap but slow. One sprints. One waits for a rock to warm up. Choose your fighter.
- Newborns & Brown Adipose Tissue: Babies can’t shiver properly. They’d die if not for brown fat. Packed with mitochondria, designed to burn energy and generate heat. It’s like a tiny internal heater installed just for infancy. Then it mostly vanishes. You spent your best heating system on being a baby and don’t even remember it.
Understand why your body never stops micromanaging, how hormones fight over your blood sugar, and why babies are born with a biological space heater.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline of this video
00:00:52 – Homeostasis
00:07:15 – Glucose & Our body
00:12:16 – Role Of Insulin
00:22:05 – Role Of Glucagon
00:27:14 – Brief Summary Page
00:29:55 – Diabetes & Long Term Consequences
00:35:07 – Type I Diabetes
00:38:00 Type II Diabetes
00:41:12 – Diabetes Summary Page
00:44:53 – Ectothermic V.S Endothermic
00:51:30 – Reducing body temperature
00:56:58 – Increasing body temperature
01:00:00 – Temperatures & Enzyme Function
01:01:19 – Newborns & Brown Adipose Tissue
01:04:13 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D3.3 - The Kidney (HL)
LECTURE VIDEO
DESCRIPTION
You have two fist-sized organs sitting behind your guts whose entire job is to judge your blood, separate the trash from the treasure, and yeet the waste into your bladder. They filter your entire blood supply 60 times a day and adjust your pee based on whether you’re a hydration legend or a dehydrated disaster.
This video tours the ultimate purification plant:
- Kidney & Nephron Structure: Kidneys are the factory. Nephrons are the million tiny workers who never call in sick, never take breaks, and definitely never talk about their weekend. Workaholics, honestly.
- Glomerulus: The pressure washer from hell. Blood gets shoved through a tangled knot of capillaries. Water, ions, and glucose squeeze out. Blood cells and proteins? Too fancy. Denied at the door. Microscopic velvet rope energy.
- Proximal Convoluted Tubule: The greedy goblin. Glucose, amino acids, useful ions—all snatched back immediately. This tubule sees waste and says “not on my watch.” Zero chill. Maximum reclaim.
- Loop of Henle: The concentration king. Dives deep, creates salt gradients, and decides whether your pee is crystal clear or looks like iced tea. Longer loop = better at saving water. Humans have medium commitment. Desert animals are extreme couponers with water.
- Distal Convoluted Tubule: The fine-tuner with anxiety. Hormones scream at it. It panics and adjusts salt and pH. Last chance to fix things before the fluid commits to being pee.
- Collecting Duct & Osmoregulation: The final boss. ADH (the “did you drink water today?” hormone) tells this duct how much water to reclaim. High ADH = dark pee, you’re dehydrated, shame on you. Low ADH = clear pee, you’re crushing it, stay hydrated king/queen.
- Blood Supply Adjustments: Kidneys also bully your blood pressure. Too low? They release renin. Hormone chaos erupts. Blood pressure goes up. Kidneys get their flow. Selfish? Absolutely. But they’re keeping you alive so let them have this.
Understand how a million tiny nephrons filter your blood like overachieving interns, why the Loop of Henle is the unsung hero of not dying of dehydration, and how your kidneys personally attack you every time you forget to drink water.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Outline Of This Video
00:00:56 – The Urinary System BIG PICTURE
00:12:18 – The Kidney Structure
00:18:00 – The Nephron Structure
00:24:48 – The Glomerulus
00:33:41 – Blood V.S Filtrate
00:37:27 – Proximal Convoluted Tubule
00:49:19 – Loop Of Henle
00:53:57 – Distal Convoluted Tubule
00:55:43 – Osmoregulation
01:00:33 – Role Of Collecting Tubule
01:08:29 – Blood V.S Filtrate V.S Urine
01:09:56 – Collecting Tube To Renal Pelvis
01:11:07 – Blood Supply Adjustment
01:16:30 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!