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Table of Contents

    1. Darwin and the Giant Tortoises
    2. Evidence of Evolution in the Rocks
    3. Layers of Rocks give us clues to their age
    4. How life started?
    5. Interpretation of the Miller-Urey Experiment
    6. How valid was the Miller Urey Experiment?
    7. DNA the blueprint for life
    8. Oxygenating the World
    9. Protista - basic unicellular organisms
    10. Protista Diversity
    11. The first Multicellular Organisms?
    12. Ctenophores and Cnidarians - first organism with real structure
    13. Cnidarians and the Fossil Record
    14. Coral Reefs under threat
    15. Test Yourself
    16. Assignments
    1. Fossil History of Marine Invertebrates
    2. Platyhelminthes: the building block for other invertebrates
    3. Platyhelminthes: a surprisingly diverse group
    4. Annelids: the first segmented animals
    5. Brachiopods: developing a bivalve shell
    6. The first Molluscs
    7. The Molluscs diversified
    8. Molluscs: Feeding mechanisms
    9. Molluscs: Evolving and keeping the shell
    10. Molluscs: Secondary loss of the shell
    11. Echinoderms: Penta-symmetrical creatures of the oceans
    12. Echinoderms: A hydrostatic structure
    13. Echinoderms diversity: variations on a theme
    14. Arthropoda: the most successful animal phylum
    15. Arthropoda: Segmentation the successful formula
    16. Early Arthropods: The fossil record
    17. Living descendents of the Trilobites
    18. Crustaceans: Arthropod success in the sea
    19. Arthropod Exoskeleton: Evolving to occupy land
    20. Test Yourself
    21. Assignments
    1. Plants: Fertilization and dispersal, the first issues
    2. Mosses: Possibly the earliest land plants?
    3. Fossils of the earliest land plants
    4. What were the earliest land animals?
    5. Living of Land: Issues of reproduction
    6. Land plants: Making their mark
    7. A Forest Environment
    8. Insects: The greatest conquerors of all?
    9. Land Plants: Still working on the reproduction issue
    10. Cycads: Getting to grips with the reproduction on land
    11. Conifers: A successful formula
    12. Earliest plant defences against herbivores
    13. Plants and Insects find "mutual benefit"
    14. Beetle pollination
    15. Plants learn to manipulate
    16. The most bizarre pollination systems?
    17. Total dependence: Yuccas and Moths
    18. Test Yourself
    19. Assignments
    1. A Tripartite body plan
    2. Chitin: A secrete ingredient for success?
    3. Issues with an Exoskeleton
    4. A "Larval Stage" leads to success
    5. Larva: Clothed in silk
    6. Metamorphosis
    7. An insect's first flying lessons
    8. Insects: Finding your soul mate
    9. An Insect's approach to rearing your young
    10. Insects: Limitations for size
    11. Insect's approach to size matters
    12. Chemical Communication
    13. Establishing a new colony
    14. The termite towers
    15. Wasp and Bee nests
    16. Dance of the bees
    17. Insect and plant cohabit
    18. Imperialism- Insect style
    19. Test Yourself
    20. Assignments
    1. Free-living chordates
    2. Fossil evidence for the first chordates
    3. A jawless predator
    4. Ostracoderms - an extinct group with heavy armour
    5. Protofish and internal bony skeletons
    6. Developing some backbone
    7. Re-inventing the cartilage skeleton
    8. Sharks and Mantas
    9. Swimbladders: refinement
    10. Test yourself
    11. Assignments
    1. The conception of lungs
    2. Possible ancestors
    3. Amphibians: The limitations
    4. A variety of habitats
    5. Colonizing the land
    6. A burrowing existence
    7. The accomplished jumpers
    8. The sticky tongue
    9. Sound production
    10. Amphibians: Mating
    11. A terrestrial environment for breeding
    12. Protecting the young
    13. Marsupial frogs
    14. Parental care: A step further
    15. Brooding in the stomach
    16. Effects of climatic conditions
    17. Moisture and development
    18. The water-holding frog
    19. Test Yourself
    20. Assignments
    1. Issues: Ectothermy vs Endothermy
    2. Breeding mechanisms of the ancestral reptile
    3. Skull structure
    4. The Anapsids
    5. The Diapsids
    6. The Synapsids
    7. First dinosaur characteristics
    8. Dinosaur fossils
    9. Gigantic herbivores and carnivores
    10. Temperature regulation limits energy use
    11. The beginning of the end for the kings
    12. Impressive parental care
    13. Conquering various living environments
    14. The flight of the dinosaur
    15. The Pterosaur: The take-off
    16. The Ptesosaurs: Not just a gliding motion
    17. The extinction
    18. Mammals' role in extinction
    19. Change in climate
    20. Crocodiles
    21. Crocodiles: Social life
    22. The Order Chelonia: Modified
    23. The lizard
    24. Modifying the scales
    25. Limb reduction
    26. Snakes
    27. Snakes: Making waves
    28. Snakes: The predator
    29. Snakes: Nurturing the young
    30. Snakes: The nocturnal hunter
    31. Test Yourself
    32. Assignments
    1. Claws for climbing
    2. Tree-perching birds
    3. Fossils of bird-like dinosaurs
    4. Weight reduction by birds
    5. The basic bird plan of structure
    6. Bill structure: Evolving
    7. Feathers: Differentiation and adaptation
    8. The structure of feathers
    9. Feather coloration: Melanins and carotenoids
    10. Feather Differentiation of plumage
    11. Feathers: Specialized
    12. The Birds of Paradise
    13. Courtship: Behavioural patterns
    14. Birds: Copulation
    15. Incubating the eggs
    16. Protecting the eggs
    17. Precocial and altricial chicks
    18. The relationship between the anatomy and flying
    19. Flight: Speed and distance
    20. Migration: A semi-annual event
    21. Losing flight
    22. Test Yourself
    23. Assignments
    1. The Spiny Echidna
    2. The loss of teeth
    3. Absorbing heat
    4. An endothermic metabolism
    5. Mammals: A polyphyletic origin
    6. The earliest true mammal
    7. The Opossums: The pouch
    8. Caring for the young
    9. Marsupial fossils
    10. Carnivorous marsupials
    11. The splitting world
    12. Evidence supporting continental drifting
    13. An alternative method of nourishing the young
    14. Placental mammals vs Marsupials
    15. Marsupials: Opportunity to evolve
    16. Survival today
    17. Marsupials and placental mammals: A resemblance
    18. Major differences
    19. The rat kangaroo
    20. Kangaroo: Escaping predators
    21. Kangaroo: The teeth
    22. Kangaroo: Reproduction
    23. The effect of drought on reproduction
    24. The placental mammals dominate
    25. The placenta
    26. The mammalian sexual cycle
    27. Immunological rejection
    28. Placental mammals: Success
    29. Test Yourself
    30. Assignments
    1. Dinosaur domination
    2. Various insect-eating mammals
    3. Shrews: Characteristics
    4. The Mole: Going underground
    5. Mole tunnels as traps
    6. Insectivores: A sticky tongue
    7. The pongolins
    8. Pongolins: Protection
    9. The armadillos: Characteristics
    10. Various species of armadillo
    11. Specialist ant-eaters: Lack of teeth
    12. Taking to the skies
    13. The Colugo: Gliding
    14. Bats: Flapping flight
    15. Bats: Saving weight
    16. Bats: Echo location
    17. Bats: Sonar equipment
    18. Methods for avoiding predation by bats
    19. Bats: Diet
    20. Meat-eating and fish-eating bats
    21. The vampire bats
    22. The Yellow-eared Bat
    23. Cetacean fossils
    24. Whales: An aquatic existence
    25. Whales: Adapting to swimming life
    26. The diet of whales and the sounds of dolphins
    27. Dolphins: A language
    28. Whales: A song
    29. Evolving communities
    30. Test Yourself
    31. Assignments
    1. Plant eaters: The teeth and digestion
    2. Elephants: Aiding digestion
    3. Compensation by plants
    4. Ruminants
    5. Animals prepare for food shortage
    6. The hibernating dormouse
    7. Flying squirrels
    8. Monkeys: Coordination development
    9. The Sloth: Characteristics
    10. The Sloth: Mating and predators
    11. The forest floor: Vegetation
    12. The large herbivore
    13. A solitary life
    14. Specialized meat-eaters
    15. Grass: Highly advanced
    16. The spread of the grassland
    17. Smaller is better
    18. Mole rats: Safety in the burrows
    19. Mole rats: Teamwork
    20. Prairie dogs: Organized social systems
    21. Prairie dogs: Selective cultivation
    22. The viscacha
    23. Placental migration
    24. Proto-horses: Lengthening the legs
    25. Proto-horses: The teeth and skull
    26. Descendants of the forest dwelling antelopes
    27. Antelope: Safety in herds
    28. Breeding arrangements
    29. The improved predator
    30. Lions: Hunting
    31. Hyenas: Communication and hunting
    32. Hyenas go zebra hunting
    33. Test Yourself
    34. Assignments
    1. An ancestor to the primates
    2. The Ring-tailed lemur
    3. The male Ring-tailed lemur: The use of scent
    4. The Ring-tail: Time in trees
    5. Infant lemurs
    6. Sifakas
    7. The Indris
    8. The nocturnal lemurs
    9. The Aye-aye
    10. Competing with monkeys
    11. The Loris: Sign posting
    12. The Tarsier
    13. Monkeys: Sight is key
    14. Monkeys: The use of colourful displays and sound
    15. Monkeys: Anatomical features
    16. Scent in communication
    17. Marmosets
    18. Adapting to great weight
    19. Prehensile tails
    20. The adaptable Macaque monkey
    21. Macaques: Behavioural patterns
    22. Bi-pedalism
    23. The Orang Utan
    24. The Orang Utan: Supporting the great weight
    25. The Orang Utan: It's repertoire
    26. The Orang Utan: Solitude and size
    27. The Gibbons
    28. Gibbons: Family life
    29. Gorillas: The use of the arms
    30. Gorillas: Family groups
    31. Similarities between Gorillas and humans
    32. Gorillas: A placid existence
    33. Chimpanzees: Their diet
    34. Chimpanzees: Maternal support
    35. Chimpanzees: A friendly gesture
    36. Chimpanzees: The toolmakers
    37. New situations lead to greater change
    38. Test yourself
    39. Assignments
    1. Characteristics of plains-living apes
    2. Development of ape men
    3. Homo erectus: Adaptation
    4. Homo erectus: Toolmaker and hunter
    5. Homo erectus: Methods of communication
    6. Recognizing one another
    7. Gestures: Providing information
    8. Homo erectus: Increase and spread
    9. A changing climate
    10. Homo sapiens
    11. Culture and cultural identities
    12. Test Yourself
    13. Assignments

Swimbladders: refinement

The other group of fish which retain bone in its skeleton, also had to overcome weight problems in the water. Early fish with heavy bone-based scales, colonized shallow lagoons and swamps which had warm, poorly oxygenated water. The bichir (Polypterus)(order Polypteriformes), a heavy scaled fish occurring in Africa indicates how these early fish overcame such problems. These animals rise regularly to the surface and take a gulp of air which goes into a pouch leading off the top part of the gut. A concentration of capillaries in the walls of the pouch absorb the gaseous oxygen. These air-filled pouches which were the first lungs also provided buoyancy and the ability to float without using the tail and eventually evolved into swimbladders. With the ability to absorb gas from the blood systems there was no need to collect air from the surface and the connecting tube to the throat became no more than a solid thread. The diffusion of gases into and the expelling of air out of the swimbladder would permit a precise means of vertical control in the water. The pectoral fins would provide refinement to this control. However, swimming skills were improved still further with increased tapering of the twin-bladed symmetrical tail that is driven by banks of muscles on either side of the backbone. Streamlining was enhanced with reduction of heavy scales into smaller tightly fitting ones that overlap like tiles of a roof and are covered by slippery mucous, and pectoral and pelvic fins being able to fold back into depressions in the lateral sides of the fish. The respiration using gills was further refined with the development of a movable, bony operculum which by inducing negative pressure forces water over the gills and improves respiration.

Nile Bichir

Nile Bichir

The bichirs are a family (Polypteridae) of archaic-looking ray-finned fishes, the sole family in the order Polypteriformes. They have thick bonelike scales and a series of dorsal finlets instead of a single fin. Their jaw structure more closely resembles that of the tetrapods than that of the teleost fishes. All 16 recognized species occur in freshwater habitats in Africa. They are popular subjects of public and large hobby aquaria.


In some Asian cultures, the swim bladder (otherwise known as fish maw) is considered a food delicacy. Usually served braised or in stews, it is rather tasteless by itself, but it is enjoyed more for its slightly rubbery and crunchy texture.

The diversity of morphological forms is testimony to the success of the group. One group, the flying fish (order Atheriniformes) leap out of the water and glide hundreds of metres in the air using the elongated pectoral fins. This may be an anti-predator tactic. Garfish (order Lepisosteiformes) have pectoral fins that have become filmy skulls rotating slowly back and forth which permits them to hover in water. Dragonfish (order Pegasiformes) have lateral fins modified into defensive mechanisms with each ray barbed with poison.

Band-wing flyingfish Cheilopogon exsiliens, with large pectoral and pelvic fins

Band-wing flyingfish Cheilopogon exsiliens, with large pectoral and pelvic fins

Garfish (Belone belone) are a pelagic, oceanodromous needlefish found in brackish and marine waters of the Eastern Atlantic and the Mediterranean Sea


The swimbladder has released fish from weight problems, and therefore, some like the box-fish (family Ostraciontidae) and sea-horse (order Gasterosteiformes) have regained armour.

The Sea Horse: Hippocampus

Seahorse (photo by NOAA)

Down the flanks and around the head of fish runs a series of pores, connected by a canal running just below the surface. This is called a lateral line and enables the fish to detect differences of pressure in water. As a fish swims, it creates a pressure wave ahead of it, when this wave meets another surface the fish can detect pressure changes created by this surface. It is this ability that permits them to detect other fish and to polarize themselves into swimming in shoals. Vulnerability to predators is thought to be reduced by shoaling.

Atlantic herring Clupea harengus on its migration to their spawning grounds in the Baltic Sea.

Underwater video (looping) of a school of Atlantic herring Clupea harengus on its migration to their spawning grounds in the Baltic Sea. With such high speed they can migrate over thousands of kilometers. Some scientists are of the opinion that cruising in a close group has advantages in the energy consumption, one fish utilizing the pressure field created by the next fish. In the North Atlantic herring cruise between Norway and Greenland every year.

Fish also have an acute sense of smell and detect minute changes in the chemical composition of water. This sense of smell may guide fish to food. Fish also detect sound with the addition of a third canal (in a horizontal plane and below the sac) which supplements the two semicircular canals that are found on either side of the skull of the lamprey. All three canals and the sac have very sensitive linings and contain small calcium particles which move and vibrate. Sound waves, which travel better in water, penetrate the semicircular canals without the need for passages which are required by terrestrial animals.

The eyespot of the lamprey is primitive compared with the bony fishes. The eye of the bony fish and higher vertebrates is a closed chamber with a transparent window and a lens in front and a photosensitive lining at the back (retina). The photosensitive lining contains two kinds of cells, rods for distinguishing light and dark and cones which are sensitive to colour. Sharks and rays lack cones and are unable to perceive colour; this may reflect the lack of highly coloured examples within the group. Bony fish have both types of cells in their retina, and are also characterized by vivid colours and striking patterns. The Butterfly fish (Family Chaetodontidae) showing particularly diverse colours and patterns which permits species recognition. Colour is also an important asset in male fish during spawning. Such displays serve to chase other male fishes away, and to attract female fish. Pigment granules diffuse within the skin as the fish become excited and fights other rivals or to stimulate a female fish to lay her eggs.

Butterfly Fish

Chaetodon lunula


Butterflyfish are named for their brightly coloured and strikingly patterned bodies in shades of black, white, blue, red, orange and yellow (though some species are dull in colour). Many have eyespots on their flanks and dark bands across their eyes, not unlike the patterns seen on butterfly wings. Their deep, laterally compressed bodies are easily noticed through the profusion of reef life, leading most to believe the conspicuous coloration of butterflyfish is intended for interspecies communication. Butterflyfish have uninterrupted dorsal fins with tail fins that may be rounded or truncated, but are never forked.

Eyes of fish have become adapted in various ways to vision below and above water. The archer fish (Toxotes jaculator) squirts fluid at an insect above the water and knocks them into the water where they can be eaten. This required compensation since light bends as it passes from water to air due to differences in density. Anableps has a horizontal division across its pupils which effectively gives it four eyes, the two lower halves for underwater use and the two upper halves for above water. Since fish can occur at great depths (below 750 m) where there is no light, they may posses modified cells producing luminescent chemicals which are activated rhythmically and may represent some form of communication to the rest of the shoal. The whiskery angler fish (Antennarius scaber) (order Lophiiformes) has a modified dorsal fin spine with an elongated thread at the end of which are cells producing luminescence. This is used to entice other fish to explore the light and be consumed.

Humpback anglerfish (Melanocetus johnsonii)


Anglerfish is the common name for the 200+ species that comprise the bony fish orderLophiiformes. They are for the most part a deep-sea fish, although there are some anglerfish families that have shallow-water representatives, and one family, the frogfishes (familyAntennariidae), occurs only in shallow water. Examples of other anglerfish families that have some shallow water species are the monkfish or goosefish, (family Lophiidae) and the batfishes (Family Ogcocephalidae). These families also have deep water representatives. The deep-sea mid-water anglerfishes belong to the suborder Ceratioidei and are usually referred to as ceratioids.

Water that is covered with floating mats of vegetation is also turbid, and in such an environment some fish have generated electricity from modified muscles in their flanks. Electrical signals are transmitted almost continuously creating flow patterns of current in the immediate vicinity. Any object encountered disrupts these flow patterns and the fish perceives these changes through receptor pores located over the body. The electric eel of South AmericaElectrophorus electricus, although not a true eel, has additional body tissues that produces a massive shock of waves with which it kills or stuns prey items.

Electrophorus elec

From the jawless armour-laden prototype fish have evolved some 30 000 different forms to occupy seas, lakes and rivers of the world.