LEC 19 Flashcards
Evidence Supporting Evolution
Theory of Evolution
- Scientific evidence indicates all living organisms on Earth are related
2.Believed that life descended from a single, simple, life-form that existed approximately 3 billion years ago
___________ of life is thought to be a result of __________
- Diversity
- evolution
Evolution three key elements
- Descent over time
- Modification
- Unpredictable and natural
Descent over time
slow change in populations over generations that makes them different from their ancestors
Modification
change in phenotype of a species related to changes to the genes of an organism (mutation) or the reshuffling of genes through meiosis
Unpredictable and natural
affected by chance, natural selection, historical events and changing environments
Evidence for Evolution (3)
- Fossils & fossil record
- Comparative anatomy, embryology & biochemistry
- Biogeography
Theory of evolution was first proposed in the mid-1800’s by _________ ___________.
Based on _________ and evidence collected and never been any credible evidence to disprove the theory.
- Charles
- Darwin
- observation
Evidence: Fossils
Preserved remains of organisms
Evidence: Fossils Process (2)
- Occurs when remnants are covered sooner after death with layers of sediment & volcanic ash
- Overtime they become mineralized and leave rock like impressions of hard tissues (bones, teeth etc.)
Evidence: Fossils Details (5)
Have fossils for over 200,000 species
Many organisms we will never have information for because no hard tissues
Richest source of information but tends to be incomplete
Determine age by radiometric dating (either K+ or C-14)
Can observe or compare changes over time in an organism
When different organisms share similar anatomical features it is usually because they came from ___________ ancestor.
common
Evidence can compare: (3)
Anatomical structures
Development of embryos
Biochemical molecules
anatomical structure types (3)
Homologous
Analogous
Vestigial
Homologous structures
Body structures that share a common ancestor
Homologous structures example
Analogous structures
Structures that serve the same function but do not arise from a common ancestor
Analogous structures example
bird and insect wing – both used for flight, however, no physiological similarities exist
Vestigial structures
Structures that serve little or no function in an organism
Maybe homologous to body parts in other organisms
Vestigial structures examples
Human tailbone (coccyx) is vestigial remains of a tail
Human appendix was once larger and had more absorption capability. Only has immune functions now.
Muscles for wiggling our ears
Wisdom teeth
Evidence: Comparative Embryology
Comparing embryos of animals
Early embryonic development is similar among vertebrates
All vertebrates develop: (3)
- Notochord – becomes the core of the intervertebral discs
- Somites – series of folds that become bone, muscle & skin
- Gill or Pharyngeal arches – become either gills or part of face, middle ear & mouth
Comparative Biochemistry
- Examines similarities between proteins and genes of different species
- When two species possess identical or nearly identical biochemical molecules, common ancestry may be indicated
- The greater the difference, the further back the divergence is likely to have occurred
Evidence: Biogeography
Study of the distribution of plants and animals around the world
What contributes to a species ability to migrate?
- Physical barriers may have prevented the spread of plants and animals from one area to another
Oceans & mountains prevent movement of some species - Environmental conditions may make it impossible for a species to survive
Too hot or cold for species to live
Continental Drift
Pangea (tectonic plates all joined 200 million years ago)
Started to drift and left related groups of organisms isolated from each other.
These organisms evolved separately, but along almost parallel lines
Evolution is the result of:
Mutations
Natural selection
Movement of organisms in/out of populations
Chance
Mutations
Random and rare changes in DNA of an organism
May result from replication “errors” and/or epigenetics that get passed on to subsequent generations
Give different form and function to the organism
An accumulation of mutations may cause one species to diverge into two distinctly different species
Theory of Evolution:
Life arose only once, probably in the primordial sea and all life as we know it descended from that early life form
Natural Selection
Darwin proposed that individuals with certain traits are more “fit” for their local environment
Since they are more “fit” to the area, they are therefore more likely to survive and reproduce (and pass on their “fit” traits to their offspring)
Natural selection usually causes beneficial alleles to increase and harmful alleles to decrease in frequency in the gene pool of a population
Genetic drift
Random changes in the allele frequency because of chance events
More likely to occur in smaller populations (more vulnerable to change) than larger ones
Genetic drift causes
Bottleneck effect
Founder effect
Bottleneck Effect
Major catastrophe occurs and wipes out most of a population
Catastrophe has no regard for any previous measure of fitness
Remaining individuals may not represent the original population nor the most “fit” genes
Founder Effect
A few individuals leave the original group and begin a new population in a different location
Environmental change that isolates a small population
New gene pool may not be representative of the original population, nor the most “fit” genes
Gene Flow
Redistribution of alleles
Caused by immigration or emigration
Results in mixing of gene pools that may not have otherwise mixed
Antigenic Shift
Affects simpler populations (like viruses)
Very rapid and dramatic change in a virus
Caused when two or more viruses combine or exchange genetic material
Forms a new virus with entirely different combination of genes that is potentially more infective than either of the two originals
Extinction
Period when the life forms die out/disappears completely
At least 5 mass extinctions over last 530 million years
Most “recent” period of extinction
end of Cretaceous period
Asteroid or comet collided with earth 65 million years ago
Thought the collision caused significant global climate change
Evolutionary Tree
Used to depict points of divergence between species
Shows time, points of extinction and adaptive radiation
Adaptive Radiation
New species develop in a relatively short period of time from a single ancestor
Shown as numerous branches on an evolutionary tree
