We are going to view several segments of the fantastic BBC documentary by Sir David Attenborough.
There are some four million kinds of animals and plants in the world - four million different solutions to the problems of staying alive. This is the story of how a few of them came to be as they are.
Life on Earth, the result of a three-year, 1.3 million mile odyssey to all seven continents, is the story of how a few of those life forms came to be as they are, not as isolated oddities but as elements in a long and continuous story that began billions of years ago.
BYERLY'S NOTES
Section 3: The First Forests - The world of plants, primitive and grand.
Download Section3.doc
3.1 The First Plants
- End of September – the first sea creatures
- Beginning of November – first life on land (simple algae) at edge of land
- Algae develops cell wall thick enough to survive on the moist boulders and gravel
- Algae still depend on presence of H2O to carry swimming sex cells and reproduce
3.2 Millipedes and Spiders
- Millipedes - Segmented bodies / vegetarians. Today only few inches long, the ancestors of a millipede may have been as long as a cow.
- Spiders – ancestors of scorpions
- Develop gland in abdomen to produce silk –for hunting; modified limbs (spinneret’s)
- Reproduction without water – how to get sperm to egg?
- Spiders – signaling ritual. Important for hunters that they send the right signal.
3.3 The First Insects
- 400 million years ago (mid November)
- They would have the air to themselves for the next 100 million years (late November)
- Not unlike silverfish
- One adaptation to move from plant to plant – wings
- Probably evolved from tiny lobes on the back – just like dragonflies today
- Reason for success?
- Dragonfly (grow wings in just one night) superb fliers – homo sapiens cannot replicate the intricate movement of insect wings
3.4 Plant Adaptations
- By the time 1st insects are in flight (over 380 mya) plants have dome out of water and are thriving on land.
- Solved problems of desiccation (aridity) and support out of water.
- Growing tall.
- Could only grow in damp places because plants still relied on h2O to carry sex cells.
- Conifers - among first to develop pollen and use the wind to transport sex cells and reproduce
- Rather haphazard system so pollen must be produced in incredible amounts
- One cone = several million grains of pollen / thousands of male cones on average tree
- Does not bode well for allergy sufferers
- Fewer female cones (the big ones). Grow on same branches but in the tips of shoot.
- Female cones grow for two years wrapping around fertilized eggs – eventually dries out and releases seeds
- Today 1/3 of forests are conifers
- giant sequoias – largest living organism seal wounds with resin
3.5 Insects in Amber (1 minute)
- lumps of resin harden into amber
- excellent adaptation for wounds – great way to see ancient insects
3.6 The Development of Insect Flight
- adaptation of bees – smaller wings, fold compactly (nesting, food sources) that must beat very fast, two pairs hooked together to form a single surface.
- adaptations of the beetles – spend time in dense vegetation and forests, first pair of wings have been converted to a protective cover, spring loaded joints in the veins of the wings fold them away when not in use. Least agile of insects in flight
- adaptations of the flies – most agile fliers. Seem to have lost rear pair of wings – evolved into little gyroscopes for aerobatic maneuver. Makes for great flying Beats wings up to 175 times per seconds.
Comments