Ch 23: Broad Patterns of Evolution

Question 1

How do the fossil record helps explain the evolution of life over billions of years?

Answer 1

• Fossil record shows the existence of great changes in the organisms over the geological time, including at different time points

Question 2

Briefly describe the evolution of life and the major events in the history of life over the past 4.6 billions of years

Answer 2

• Fossil record helped define a geologic time of life on earth: the geological record.
  
  • Early prokaryotes at ~3,5 billions years ago: cyanobacteria & other photosynthetic species
  • Atmospheric oxygen increase significantly at ~2,7 billions years ago
  • Single-celled eukaryotes at ~1,8 billion years ago
  • Multicellular eukaryotes at ~1,3 billion years ago
  • Animals at ~0.7 billion years ago

Question 3

Explain how speciation and extinction working together affect life diversity.

Answer 3

• As a population increases in size when there are more births than deaths, the rise of a group of organisms occurs when more new species are produced than are lost to extinction. The reverse occurs when a group is in decline.
  
  • Mass extinctions
  • Plate Tectonics
  • Adaptive Radiations

Question 4

Explain how earth geological events, such as plate tectonics, asteroids fall, can lead to species extinction.

Answer 4

• One reason for this is that continental drift alters the habitats in which organisms live.
  
  • Overall, the formation of Pangaea greatly altered the physical environment and climate, which drove some species to extinction and provided new opportunities for groups of organisms that survived the crisis.

Question 5

What are mass extinctions? Is there a sixth mass extinction in progress nowadays?

Answer 5

Mass extinctions - The elimination of a large number of species throughout Earth as a result of global environmental changes

There could be a sixth mass extinction and it would be caused by human activities

Question 6

Explain how mass extinctions can be detrimental but also beneficial to the evolution of life.

Answer 6

A mass extinction can reduce a thriving and complex ecological community to a pale shadow of its former self. By eliminating so many species, mass extinctions can pave the way for adaptive radiations, in which new groups of organisms proliferate.

Question 7

Explain what adaptive radiation means and how it supports the diversification of life on earth.

Answer 7

• Adaptive radiation = evolution of many diversely adapted species from common ancestor. may follow:
  
  • Mass extinctions
  • The evolution of novel characteristics
  • The colonization of new regions

Question 8

Explain the major intrinsic biological mechanisms, i.e. genetic variations, underlying life evolutionary changes observed in the fossil record.

Answer 8

• Importance of developmental genes:
  
  • Morphological differences can arise from genes altering the:
    
    • Heterochrony → An evolutionary change in the rate or timing of developmental events
    • Paedomorphosis → The retention in an adult organism of the juvenile features of its evolutionary ancestors
    • Spatial pattern of development → Homeotic genes (Example hox genes) : master regulatory genes that control spatial organization of body parts
      
      • Changes in gene sequence
      • Changes in gene regulation

Question 9

Connect macroevolution and microevolution, and explain why/how macroevolution allows to understand that evolution is not goal oriented.

Answer 9

Macroevolution teaches us about microevolution; Evolution is NOT goal oriented; Evolutionary trends do not imply an intrinsic drive toward a particular phenotype; Evolution results from interaction between organisms and their current environments

Question 10

NOTES

Answer 10

• Developmental genes affect morphological differences between species by influencing the rate, timing, and spatial patterns of change in an organism’s form as it develops into an adult. The evolution of new forms can be caused by changes in the nucleotide sequences or regulation of developmental genes called Hox genes.
• One of the most common techniques for determining the age of fossils is radiometric dating, which is based on the decay of radioactive isotopes. In this process, a radioactive “parent” isotope decays to a “daughter” isotope at a characteristic rate. The rate of decay is expressed by the half-life, the time required for 50% of the parent isotope to decay.
• Many striking evolutionary transformations are the result of heterochrony, an evolutionary change in the rate or timing of developmental events.
• Exaptations are structures that evolve in one context but become co-opted for another function.
  • Note that the concept of exaptation does not imply that a structure somehow evolves in anticipation of future use.