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
Adaptations to temp on land being highly variable
Animals - burrow or rest in shade, become nocturnal, sweat glands, fur feathers, migration, hybernation
Plants - evaporative cooling through pores, develop spores that can persist through cold/dry periods,
Consequence of a vertebrate centric point of view
- much of the earths history has been assigned names based on newly derived vertebrates, the vertebrate did not dominate the dominate the landscape but instead say a rise in its own diversity
Once life on land had taken hold
- the majority of new niches had been created
- with no new niches there were no drastic changes in morphology or body plans
Life has increased and decreased in diversity
- a steady rate of extinction and five major extinction events (life finding new ways to solve the same problem)
percentage of animal species that are inverts
99%
side note - we discover new species every year
Golden age of species recovery
What we’re in now, but biodiversity is under a threat globally
p.s. 25% of all known amphibian species were discovered in the last 10 years, since 93 the # of known mammal species increased by 10%
How can we conclude we’re in the most diverse point in time
By combining statistics, the fossil record, and current known numbers of species
Majority of new animals being discovered are
insects (mostly beetles)
6th major extinction event fun facts
- we’re in it
- rate of extinction is now 100 times greater than naturally, by some estimates
