lecture 12 Flashcards
When multicellular organisms originate from (Historically)
End of precambrian, start of Paleozoic
The earliest known occurrence of multiceullar animals are the _________
Some of them resemble ________
- Ediacaran fauna
- modern jelllyfish and segmented worms
study of early diversity of life dependent on
DNA evidence can offer _______
fossil evidence
hints with respect to timeline
Sedimentary rock
- preserves fossils
- pile up over geologic time and become rock
Factors that create a high chance of preservation
- being buried quickly
- having hard parts
Law of superposition aids in _______
determining the relative age of fossils
Modernly, fossils can be dated with ______
elemental isotopes, in accompanying rock
Half-life
Length of time required for exactly one half of original isotope to decay
Half-life determination technique
Measure amount of original(mother) isotope as well as amount of decay(daughter) isotope
The radioisotope is the ___________
The decay product is the ________
parent isotope
daughter isotope
Beginning of Cambrian period introduced
a major increase in the diversity of animal species
- including all invertebrates we see today
- 100 animal groups(30 still today)
The Burgess shale is
a highly unusual preservation of soft bodied organisms
Biota of burgess shale
typical of cambrian deposits
Hard-part bearing organisms of burgess shale
make up as little as 14% of the community
Burgess shale biota has a range of
60% _____
30% __________
10% _______
free swimming organisms & common bottom dwelling organisms
60% feed on organic content on sea floor
30% filter particles from the water
10% predators or scavengers
Two hypothesis for cause of Cambrian Explosion
- Advances just before the explosion allowed subsequent groups to exploit new environments and rapidly adapt to them
- Diversity may be related to rising oxygen levels(They had high oxygen levels then)
Mid-Ordovician characteristics
- warm and humid
- marine invertebrates very diverse
- ancestral jawless fish present
- invasion of land by plants and arthropods (set of new environments)
Land plant evolution fun facts (4)
- evolved 472 million years ago
- lack stems or roots
- very important evolutionary breakthrough
- shared a common ancestor with the modern order of Coleochaetales(algae)( also bryophytes)
- evidence for the relationship found in morphology and genetics
Bryophytes
all land plants with no true vascular tissue (non-vascular plants)
Pneumodesmus newmani
- oldest hard body creature to live on land
- 428 million years ago
- late silurian
Challenges to living on land
- Gravity requires some rigidity
- Water is no longer everywhere
- Obtaining sufficient energy
- Temp on land is highly variable compared to water
Adaptations to gravity on land
Animals - muscles and skeletons to move on land
Animals - roots for anchoring, rigid cells to maintain vertical stance
Adaptations to water not being everywhere on land
Animals - Outer layer that prevents inner tissues from drying out
Plants - Waxy cuticle to retain water, use roots to obtain ground water
Adaptations to obtaining sufficient energy
Animals - are heterotrophs and develop new means of eating plants and other animals
Plants - grow upright to obtain sufficient sunlight for photosynthesis, requires support tissue
