1.4 Evolution Flashcards
What is life’s unity?
- cells form the basic unit of all life
- DNA, RNA, and proteins carry out the molecular functions of all cells
- metabolic reactions build and break down macromolecules
What is evolution?
changes in the genetic make-up of populations over time, sometimes resulting in adaptation to the environment and the origin of new species
explains the unity and the diversity of life
What does variation in populations provide?
the raw material for evolution
What is natural selection?
the process in which, when there is genetic variation in a population of organisms, the variants best suited for growth and reproduction in a given environment contribute disproportionately to future generations
of all the evolutionary mechanisms, natural selection is the only one that leads to adaptations
Give some examples on what evolution has done.
- how people around the worlds have developed breeds of dogs
- why antibiotic resistance is on the rise in many disease-causing microorganisms
What may be life’s most fundamental property?
the capacity for Darwinian evolution; life has been shaped by evolution since its origin
What arse the 2 categories of the causes of variation among individuals within a species?
environmental variation and genetic variation
What is environmental variation?
variation among individuals due to differences in the environment
ie. sunlight/shade, insects
What is genetic variation?
differences in genotype/genetic material that is transmitted form parents to offspring, among individuals in a population
What do differences among individuals’ DNA lead to?
differences among the individuals’ RNA and proteins, which affect the molecular functions of the cell and ultimately can lead to physical differences that we can observe
ie. different taste, colour, size
What does fertilization do?
produces unique combinations of genes, which explains in part why sisters and brothers with the same parents can be so different from one another
What does genetic variation stem from?
ultimately from mutations
How do mutations arise?
either from random errors during DNA replication or from environmental factors such as UV radiation, which can damage DNA
What happens if mutations aren’t corrected?
they are passed on to the next generation
Describe the difference between mutations that:
- harm growth and reproduction
- are neither harmful nor beneficial
- are beneficial to growth and reproduction
in nature, most mutations that harm growth and reproduction die out after a handful of generations
those that are neither harmful nor beneficial can persist for hundreds or thousands of generations
those that are beneficial to growth and reproduction can gradually become incorporated into the genetic makeup of every individual in the species
this is how evolution works: the genetic makeup of a population changes over time
What does evolution predict?
a nested pattern of relatedness among species, depicted as a tree
What does the evolutionary theory predict?
- new species arise by divergence of populations through time from a common ancestor
- closely related species are likely to resemble each other more closely than they do more distantly related species
- primates show a nested pattern of similarity, and this is what morphological and molecular observations reveal
- we can continue to add other mammals and then other vertebrate animals to our comparison, in the process generating a pattern of evolutionary relationships that forms a larger tree, with the primates confined to one limb
What is the tree of life?
what biologists call the full set of evolutionary relationships among all organisms
*figure 1.17 textbook
Describe the tree of life.
- two branches: Bacteria, and Archaea and Eukarya
- although eukaryotes include large multicellular organisms such as humans, most branches on the tree consist of microorganisms
- last common ancestor of all living organisms, which forms a root to the tree, is thought to lie between the branch leading to Bacteria and the branch leading to Archaea and Eukarya
*figure 1.17 textbook
Describe Eukarya in the tree of life.
- shows that eukaryotes arose form within the Archaea, but origin of eukaryotic cells may be more complicated than that
- Eukarya is now thought by many biologists to have originated from a partnership, or symbiosis, between an archaeon and a bacterium
*figure 1.17 textbook
What is one feature of the tree of life that everyone accepts?
plants and animals so conspicuous in our daily existence make up only two branches on the eukaryotic limb of the tree
What does the tree of life make predictions for and how?
for the order of appearance of different lifeforms in the history of life, documented in rock in the fossil record
What does the greater tree predict?
- that humans should appear later in the fossil record than monkeys
- that primates more akin to lemurs and tarsiers should appear even earlier
- that all records of animal life should be preceded by a long interval of microbial evolution
these predictions are confirmed by the geologic record
What is “descent with modification”?
evolutionary changes that have accumulated over time since the two lineages split
