11. Changes In Biodiversity Over Time Flashcards
Define evolution
The gradual adaptive change over geological time, in the composition of populations from ancestral species to new species
Micro evolution
Small scale changes within a gene pool of a population of a species over time
Macro evolution
Large scale changes involving species and a genera over time. New species evolve whilst others become extinct
How old is the earth
4500 million years old
Define stratigraphy
Technique used, where the relative age of a fossil can be determined by the position of that stratum
What is stratification
Process of formation of layers in sedimentation rock
What does the principle of superposition state?
older layers of rock are at the bottom of a sequence of strata and are overlain by progressively younger layers
How does stratigraphy give a relative age?
this method of dating rocks gives the relative are of a rock layer (stratum) compared to other layers. For rock layers or strata, the oldest stratum is found at the bottom and the youngest at the top
What are index fossils
Fossils of species that existed during limited periods of geologic time, and are only found in restricted depth of sedimentary rock strata and thus are used as guides to the age of the rocks in which they are preserved..
-Presence of index fossils in rock strata from different parts of the world will be deemed to have the same age
What are the best index fossils
- Abundant
- Distinct from other flora or fauna
- Geographically widespread
- Found in many kinds of rocks
- Narrow in stratigraphic range
Radiometric dating
Technique in which the actual age of the fossils and rocks is expressed in years
How does radiometric dating work
Elements, known as parents contain radioactive isotopes that spontaneously decay (breakdown) to form stable daughter products
-The time of decay for each isotope is specific and the half life is the time taken for half the original radioactive isotope to decay
Carbon 14
Nitrogen 14
Uranium 235
Lead 207
Potassium 40
Argon 40 used to date rocks 3 million years old
Rubidium 87
Strontium 87
Half life carbon 14
5,730 years. Time taken for half the amount to decay to nitrogen 14
How can carbon dating be used
- Living things contain some carbon 14 in their organic material
- The ratio of carbon 1 4 12 is constant in an organism during life but after death c14 decomposed due to radioactive decay but c12 remains constant
- The longer dead the lower amount of c14 to c12, lower ration of c14 to c12
Difference between mineralised fossil and impression fossil
Mineralised fossil is where the organic matter of the structures is replaced by minerals
Impression fossil is where the organic matter has disappeared and the organism exists as an impression
Trace fossils
Preserved evidence of the activities of organisms such as footprints, tooth marks, track, burrows and fossilised dung
Biosignatures
A biosignature is a physical or chemical sign preserved in minerals, rocks or sediments that can be inferred to be cellular or have resulted from the metabolic activities or an organism
Best environments for fossil formation
Marine freshwater then terrestrial
Steps in fossil formation
- THe organism dies and is buried rapidly (ash, sediments, mud) protecting it from SCAVENGERS and DECAY
- Rate of decay slowed in REDUCED OXYGEN, LIGHT and TEMPERATURE
- Layers of material build up EXERTING PRESSURE on the remains
- The weight of which COMPRESSES original sediment layer so it becomes rock.
How does a mould form?
Organism decomposes slowly and leaves a cavity called a mould. Mould is filled wiht minerals and hardens to form a cast
3D model of original organism and original tissue replaced by carbon or minerals
The fossil is buried by more layers to form rock in right temp and pressure. More strata
How do imprints form?
Imprints of the organisms can also fossilise. Where the imprint is preserved due to sediments filling and overing the imprint with later pressure resulting i rock formation. Later erosion of upper layers may expose a lower harder layer with imprint
Where are most fossils found?
Most fossils are found in sedimentary rock, limestone sandstone, mudstone. but fossilisation can occur in ice due to action of volcanic ash.
Why is the fossil record not complete?
- Not all organisms die n areas that favour fossilisation ( oxygen and temperature too high, organisms decomposes)
- Scavengers and decomposers consume or destroy the organism, fossilisation will not occur.
- Soft bodied organisms are usually not preserved, bc not easily mineralised and do not fossilise due to decay. Decompose rapidly.
- Earth movements and lava destroy fossils or make them inaccessible
What can be concluded from the fossil record?
- Structure and arrangement of skeleton or bones suggest shape, size, mode of locomotion and nature of organisms habitat
- Structure and arrangement of teeth suggests diet and type of organism by comparing it to modern resembling organism
- Evolution of species occurs from simple to more complex forms
What is a transitional fossil?
If a new species evolved from ancestral species some intermediate fossil evidence must exist that has features of both ancestral and present forms of the species.
Archaeopteryx
- Earliest known bird fossil found.
- Had feathers, furcula (wishbone), which is also found in modern birds but also it had teeth in its beaks, claws on its wings and a long jointed bony tail, features that belong to modern reptiles
Homology structures
Structures that are similar in structure but can sometimes serve a different function
How can structural homology be seen in vertebrates?
- All vertebrates evolved from a common ancestor
- Pentadactyl limb found on most vertebrates has the same general structure
- Evolution occurs by modification of preexisting structures, not by production of totally new ones
Vestigial organs
If organisms are related by evolutionary descent it is expected that some organisms will show the presence of functionless organs that were present and functional in ancestors.
Common features in vertebrate embryo
- Pharyngeal arches present in all vertebrate embryos but develop into different structures in adults, in fish to gills, reptiles into lower jar and in mammals lower something and ear
- Tails
Basic principle of biogeography
Entails that each plant and animal species originated only once. The place where this occurred in the central origin
What can be predicted via biogeographic distribution
- Native species in different isolated regions will be distinctive bc each group evolved from a different ancestral species.
- Modern species native to a given region will be more similar to species that lived in that region in the geological past that to modern species living in a distant region with similar environmental conditions
- Same ecological niche in different isolated regions will be occupied by different species that are descended from different ancestral species that once lived in that region
Divergent evolution
Occurs when closely related species become more dissimilar over times usually in response to different environmental conditions and selection pressures.
Adaptive radiation
Special case of divergent evolution in which a large number of species, each occupying a different niche, evolved over geological time from a single ancestral species
Convergent evolution
Over geological time, natural selection may act on distantly related species to produce superficial similarities that are not due to a shared ancestry but reflect the fact that the species are adapted to a similar way of life, are exposed to similar selection pressures and occupy the same niche in their ecological communities
Analogous structures
Features that are similar in structure and function but have arisen independently (not from a common ancestor) are analogous
Extinction
End of a species. Moment of extinction is the death of the last individual of that species (although capacity to breed and recover may have been lost before that point)
Mass extinction
Period in the geological history of Earth when abnormally high number of species die out over a relatively short time frame
How do mass extinctions create great evolutionary opportunity for surviving species
They are able to diversify and undergo adaptive radiation in which the survivors expand into ecological niches that were left free with the loss of other species
Extinction occurs when…
Suitable adaptations are not present in a species when the environment changes.
- The species can no longer compete with another species for resources
- It either evolves into a new species or it and its lineage become extinct
