Download Evolution Chap24-26

Evolution Chapters 24-26
Chapter 24 – Speciation
1. Biological Species Concept: a species is a group of populations whose members have the potential
to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with
members of other populations.
2. Limitation of biological species concept:
a. Biologists cannot apply it to taxons only having asexual reproduction (archaea and bacteria)
b. Some gene flow does occur between species. For example, grolar bear (male grizzly and
female polar bear).
3. The morphological species concept defines a species by structural features
4. Reproductive isolation is the existence of biological factors (barriers) that impede two species from
producing viable, fertile offspring
5. Hybrids are the offspring of crosses between different species. For example, mule.
6. Reproductive isolation can be prezygotic (before fertilization) or postzygotic (after fertilization).
7. Prezygotic barriers:
a. Habitat isolation: aquatic or terrestrial (land), on trees or on land
b. Temporal isolation: breeding seasons different
c. Behavioral isolation: changes in courting
d. Mechanical isolation: physical changes leading to incompatibility of successful mating.
e. Gametic isolation: changes in gametes, do not recognize one another
8. Postzygotic Barriers:
9. Reduced hybrid viability: Hybrids survive less and cannot establish as a separate population.
10. Reduced hybrid fertility: Hybrids are physically fit but are not fully fertile.
11. Hybrid Breakdown: Some hybrids are viable and fertile in first generation but when mate with one
another or one of the parent species, offspring are weak and sterile.
Chapter 25 – Macroevolution
12. Fossil record shows very different organisms than living today. The fossil records show
macroevolutionary trends over large spans of time. For example, emergence of terrestrial vertebrates
and impact of mass extinctions.
13. Complete fossil records of different stages of evolution of Camel, horse, elephant and whale are
available. Scientists are adding new fossils for human, dinosaur and bird evolution.
14. Stromatolites are layered rocks formed by mineralization of thin layers of sediments bound by
prokaryotic organisms.
Origin of Life:
15. Earth and the other planets in the solar system formed about 4.6 billion years ago, condensing from a
vast cloud of dust and rocks surrounding the young sun.
a. The planet was bombarded by huge bodies of rock and ice left over from the formation of the
solar system.
b. These collisions generated enough heat to vaporize all available water and prevent the
formation of the seas.
c. This phase ended about 4.2 to 3.9 billion years ago.
16. The first atmosphere may have been a reducing atmosphere thick with water vapor along with
nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide.
17. Similar compounds are released from volcanic eruptions today.
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Researchers suggest that there were four main stages in this process:
1. The abiotic synthesis of small organic molecules (monomers); in small puddles of water or
near hydrothermal vents in sea or from space.
2. The joining of monomers into macromolecules; Urey-Miller experiment
3. The packaging of these molecules into protocells, droplets with membranes that maintained a
distinct internal chemistry. The protocells could show elementary reproduction.
4. The origin of self-replicating molecules that eventually made inheritance possible. RNA can
act as enzyme (ribozyme) and also act as genetic material (in RNA viruses). At first RNA
acted as genetic material but later RNA provided the template for DNA. DNA proved to be
more stable and efficient genetic material.
18. Life originated about 3.85 billion years ago.
19. Radiometric Dating of rocks/fossils: Radioactive isotopes ( C-14, U-238) decay by α and β radiations
and change into different type of atoms. U-238 ultimately changes into Lead – 206. Radioactive
isotopes always decay at a constant rate and Half-life period. C-14 decays into half mass in 5730
years. U-238 has a half - life period of 4.5 billion years. By knowing quantity of parent isotope and
daughter isotope age of rock can be determined. Fossils present in a sedimentary rock were trapped
in it during formation of the rock.
The Geological Record
20. The geologic record is divided into Eons, Eras, Periods and Epochs.
21. Eons: Hadean (4600mya), Archaean (3850mya), Proterozoic (2500mya) and Phanerozoic (542mya to
present)
22. Phanerozoic eon has 3 Eras
23. Palaeozoic Era 542-251mya: sudden increase in fossils of animal phyla and evolution of fishes and
amphibians. Origin of reptiles and present groups of insects
24. Mesozoic Era 251-65.5mya: age of reptiles, evolution of dinosaurs, origin of gymnosperms, origin of
mammals
25. Cenozoic Era 65.5mya to present: age of mammals and flowering plants, dominance of insects
continued
26. Eras are divided into Periods. Proterozoic era has only ‘Ediacaran’ period from 635-542mya. It
indicates origin of algae and soft bodies animals.
27. Palaeozoic era has 6 periods starting with COSDCP letters. Cambrian is first period and Devonian is
last period.
28. Mesozoic has 3 periods Triassic, Jurassic and Cretaceous. Dinosaurs dominated in Jurassic period.
29. Cenozoic era is divided into Palaeogene and Neogene periods. Only in Cenozoic era periods divided
into Epochs. Palaeocene is oldest epoch and Holocene is the present epoch.
30. Humans appear in Pleistocene epoch 1,8mya. Holocene represents historical time of last 100,000
years.
31. Origin of Eukaryotes through Serial Endosymbiosis:
32. Ancestral prokaryote develops infolding of membranes to form endoplasmic reticulum, Golgi
apparatus and nuclear envelope.
33. Ancestral cell with nucleus and ER picked up aerobic bacteria by endocytosis. These developed into
mitochondria. These evolved into heterotrophic eukaryotes like protists, fungi and animals.
34. Some heterotrophic eukaryotes picked autotrophic prokaryote by endocytosis. These prokaryotes
developed into chloroplasts. This eukaryotic ancestor gave rise to algae and plants.
The origin of multicellularity:
35. The evolution of eukaryotic cells allowed for a greater range of unicellular forms
36. A second wave of diversification occurred when multicellularity evolved and gave rise to algae,
plants, fungi, and animals
The colonization of land:
37. Fungi, plants, and animals began to colonize land about 500 million years ago
38. Vascular tissue in plants transports materials internally and appeared by about 420 million years ago
Plate Tectonics:
39. Earth’s crust is composed of plates floating on Earth’s mantle. Tectonic plates have formed a
supercontinent 3 times (1.1 billion, 600 million and 250 million years ago).
40. Consequences of continental drift: Formation of the supercontinent Pangaea about 250 million
years ago had many effects
a. A deepening of ocean basins
b. A reduction in shallow water habitat
c. A colder and drier climate inland
41. It led to specialization of environment and led to formation of new species and higher taxa (taxons).
42. Later supercontinent Pangaea divided into present continents and it further helped in specialization
of habitat on them and led to more adaptive radiation of taxa.
Mass Extinctions:
43. Overwhelming number of species lived in past are now extinct. Extinction of species takes place if
populations of species cannot adapt to changes in environment or changes into a new species. Five
times dramatic extinctions occurred eliminating at least 50% of total species living on earth.
44. Permian mass extinction, 251mya, is mother of mass extinctions and claimed 96% species due to
massive volcanic eruption in Siberia. Cretaceous mass extinction 65.5mya due to meteorite hit and
caused elimination of 50% of marine species and many terrestrial families of plants and animals.
45. Mass extinctions shape macroevolution.
46. Adaptive Radiation is origin of large number of taxons in a short duration. Adaptive radiation of
reptiles occurred after Permian mass extinction. Adaptive radiation of mammals took place after
Triassic mass extinction.
47. Adaptive Radiation of Silversword Alliance plants from North American relative tarweed took place
in Hawaiian Islands.
48. Changes and Regulation of Development Genes:
49. Major changes in body can result from changes in the sequence and regulation of development
genes.
50. Changes in rate and timing of developmental events result in relative growth of different parts.
Development of human and chimp skull from similar origin.
51. Changes in regulation of development genes led to elimination of limbs or fins. For example, 3 spine
stickleback fish
52. The Complexity of Eye in Mollusca and The branched evolution of horses study from images.