All courses · foundation course
Organismal Biology
An introductory course for first- and second-year students. It starts with the problems every organism has to solve and the diversity of ways life solves them, then takes the animal body one system at a time (control, circulation, breathing, digestion, salt and water, immunity, muscle, reproduction and development) and ends with how plants grow, move water and sugar, feed, sense and reproduce.
6 units · 26 lessons
Unit 1 · Organisms and their diversity
- Unit 1: Organisms and their diversity What an Organism Has to Do A barley leaf cannot take in carbon dioxide without letting water out. How do plants live with that trade?
- Unit 1: Organisms and their diversity Size, Scale and Surface A 70 kg human burns far more energy than a 30 g mouse, yet each kilogram of mouse burns about seven times more. Why?
- Unit 1: Organisms and their diversity Microbes, Protists and Fungi A methane-making microbe and E. coli look alike under a microscope. Their ribosomal RNA says they are about as far apart as either is from a yeast.
- Unit 1: Organisms and their diversity Animal Body Plans A slipper snail's mouth forms from the first opening of its embryonic gut. Its anus appears about 12 days after fertilization, from different cells. Does that make it a protostome?
- Unit 1: Organisms and their diversity Plants on Land The green cushion of moss on a wall is haploid, like a human egg. So where is the diploid moss?
Unit 2 · Control and constancy
- Unit 2: Control and constancy Tissues, Organs and Homeostasis In a room heated close to the boiling point of water, the thermometer under a man’s tongue barely moved. What was holding it there?
- Unit 2: Control and constancy Nervous Control: A First Look In 1850 Helmholtz timed a signal running along a frog's nerve. It was fast, but no faster than a car on a motorway.
- Unit 2: Control and constancy Hormones and the Endocrine System A rooster's testis, moved to his belly and cut off from its original nerves, still kept him crowing. What was it sending?
- Unit 2: Control and constancy Metabolic Rate and Body Temperature A desert iguana basking in the sun can be warmer than you are. So what does 'cold-blooded' mean?
Unit 3 · Supply and exchange
- Unit 3: Supply and exchange Circulation and the Heart An adult human holds about 5 litres of blood, yet at rest each side of the heart pumps about that much every minute. Where does it all go?
- Unit 3: Supply and exchange Blood Vessels, Blood and Lymph Halve the radius of one arteriole and the blood flowing through it falls to one sixteenth. Why so much?
- Unit 3: Supply and exchange Gas Exchange and Breathing Water holds far less oxygen than air, yet a trout's gill can bring its blood close to the oxygen partial pressure of the incoming water. Your lung cannot do that with air. Why not?
- Unit 3: Supply and exchange Carrying Oxygen and Carbon Dioxide Antarctic icefish have no working hemoglobin. Without hemoglobin, your blood would carry only about 1.5 percent of its oxygen.
- Unit 3: Supply and exchange Digestive Systems and Nutrition A dog eats a meal that falls out of its neck before it reaches the stomach, yet its stomach pours out acid. What told the stomach to start?
Unit 4 · Water, salts and wastes
- Unit 4: Water, salts and wastes Osmoregulation and Nitrogenous Waste A seabird that takes in seawater or a salt load faces a problem: bird kidneys cannot make urine as salty as the sea. Where does the extra salt go?
- Unit 4: Water, salts and wastes The Kidney Your kidneys filter about 180 litres a day and you make about one or two litres of urine. Where does the rest go?
Unit 5 · Defense, movement and reproduction
- Unit 5: Defense, movement and reproduction Innate Immunity A transparent water flea swallows yeast spores, and its blood cells swallow the spores back. Who wins decides whether the flea lives.
- Unit 5: Defense, movement and reproduction Adaptive Immunity About 150 antibody gene segments can be combined into well over a million different antibodies. Who chooses which one you make?
- Unit 5: Defense, movement and reproduction Muscle, Bone and Movement A blowfly's flight muscles contract many times for each nerve impulse they receive. How can a muscle outrun its nerve?
- Unit 5: Defense, movement and reproduction Animal Reproduction A monkey's pituitary could not sustain its output on a steady drip of the hypothalamic hormone, yet sustained it when the same hormone was given once an hour. Why does timing matter?
- Unit 5: Defense, movement and reproduction Animal Development Hold a sea urchin egg's membrane at a positive voltage and sperm usually cannot get in. Why would voltage matter to a sperm?
Unit 6 · How plants work
- Unit 6: How plants work Plant Body and Growth A 300-year-old oak still has tips that grew this spring and a ring of wood laid down this summer. How?
- Unit 6: How plants work Moving Water and Sugar in Plants A coast redwood lifts water more than 100 m with no pump at all. Where does the force come from?
- Unit 6: How plants work Soil, Nutrients and Partners Peas grown in sterile sand with a little soil extract and no nitrogen fertiliser ended up richer in nitrogen than their seeds. Where did it come from?
- Unit 6: How plants work Plant Hormones and Responses Light an oat seedling from one side and it bends toward the lamp. The tip senses the light, yet the bend forms lower down. What told it?
- Unit 6: How plants work Flowers, Seeds and Fruit Every pollen grain delivers two sperm, and in a flowering plant both of them fertilize something. Why two?