1.4 Evolution

Question 1

What is life’s unity?

Answer 1

• 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

Question 2

What is evolution?

Answer 2

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

Question 3

What does variation in populations provide?

Answer 3

the raw material for evolution

Question 4

What is natural selection?

Answer 4

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

Question 5

Give some examples on what evolution has done.

Answer 5

• how people around the worlds have developed breeds of dogs

- why antibiotic resistance is on the rise in many disease-causing microorganisms

Question 6

What may be life’s most fundamental property?

Answer 6

the capacity for Darwinian evolution; life has been shaped by evolution since its origin

Question 7

What arse the 2 categories of the causes of variation among individuals within a species?

Answer 7

environmental variation and genetic variation

Question 8

What is environmental variation?

Answer 8

variation among individuals due to differences in the environment

ie. sunlight/shade, insects

Question 9

What is genetic variation?

Answer 9

differences in genotype/genetic material that is transmitted form parents to offspring, among individuals in a population

Question 10

What do differences among individuals’ DNA lead to?

Answer 10

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

Question 11

What does fertilization do?

Answer 11

produces unique combinations of genes, which explains in part why sisters and brothers with the same parents can be so different from one another

Question 12

What does genetic variation stem from?

Answer 12

ultimately from mutations

Question 13

How do mutations arise?

Answer 13

either from random errors during DNA replication or from environmental factors such as UV radiation, which can damage DNA

Question 14

What happens if mutations aren’t corrected?

Answer 14

they are passed on to the next generation

Question 15

Describe the difference between mutations that:

• harm growth and reproduction
• are neither harmful nor beneficial
• are beneficial to growth and reproduction

Answer 15

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

Question 16

What does evolution predict?

Answer 16

a nested pattern of relatedness among species, depicted as a tree

Question 17

What does the evolutionary theory predict?

Answer 17

• 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

Question 18

What is the tree of life?

Answer 18

what biologists call the full set of evolutionary relationships among all organisms

*figure 1.17 textbook

Question 19

Describe the tree of life.

Answer 19

• 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

Question 20

Describe Eukarya in the tree of life.

Answer 20

• 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

Question 21

What is one feature of the tree of life that everyone accepts?

Answer 21

plants and animals so conspicuous in our daily existence make up only two branches on the eukaryotic limb of the tree

Question 22

What does the tree of life make predictions for and how?

Answer 22

for the order of appearance of different lifeforms in the history of life, documented in rock in the fossil record

Question 23

What does the greater tree predict?

Answer 23

• 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

Question 24

What is “descent with modification”?

Answer 24

evolutionary changes that have accumulated over time since the two lineages split

Question 25

How can evolution be studied?

Answer 25

by experiments

• bacteria are ideal for these experiments because they reproduce rapidly and can form populations with millions of individuals
• large population size means that mutations are likely to form in nearly ever generation, even though the probability that any individual cell will acquire a mutation is small

Question 26

Richard Lenski evolution experiment. Can evolution be demonstrated in the lab?

Answer 26

figure 1.18 textbook

evolution occurred in the population: E. coli bacteria evolved an improved ability to metabolize glucose

Question 27

What do experiments in laboratory evolution do?

Answer 27

• help us understand how life works, and they have an immensely important practical side
• allow biologists to develop new and beneficial strains of microorganisms that, for example, remove toxins from lakes and rivers
• show how some of our worst pathogens develop resistance to drugs designed to eliminate them