Human Evolution

Question 1

What are the 6 reasons why humans are vulnerable to diseases?

Answer 1

1. pathogens evolve faster than hosts
2. natural selection lags behind environmental change
3. trade offs make it nearly impossible for natural selection to solve certain biology problems
4. species evolution history puts constraints on potential changes from natural selection
5. some traits increase reproductive fitness at cost of increasing vulnerability to disease
6. what may appear to be a disease may really be an adaptation

Question 2

Natural selection in the pathogens favors mutations that allow 2 things. What are they?

Answer 2

1. Pathogens to use host’s resources to copy themselves more efficiently
2. pathogens to invade the immune system effectively

Question 3

When a new infection starts, the immune system learns to recognize key ____ of pathogens and produce ___ that latch onto them

Answer 3

key molecular features, produce antibodies

Question 4

What are the 3 reasons for rapid selection in pathogens?

Answer 4

1. huge capability to reproduce
2. high mutation rate of many pathogens –> lateral gene transfer for viruses & bacteria
3. huge amount of genetic variation available

Question 5

What is virulence?

Answer 5

ability of pathogen to cause disease

Question 6

Virulence is driven by pathogen’s use of _____ to replicate.

Answer 6

Host’s resources

Question 7

What determines the overall fitness of pathogens?

Answer 7

1. reproduction within a host

2. transmission to other hosts

Question 8

What can cause pathogens to fail to reproduce and spread?

Answer 8

If a pathogen is too virulent and kills the host, the pathogen fails to spread to new hosts, which decreases its fitness

Question 9

What is one way that pathogens are prevented from moving from one host to another?

Answer 9

improving hygiene

Question 10

Define resistance.

Answer 10

Capacity of pathogens to defend against antibiotics or other drugs

Question 11

As long as bacteria are exposed to sublethal doses of the antibiotic… (complete the sentence about what happens to resistant strains of the bacteria)

Answer 11

…resistant strains outcompete susceptible ones and resistant genotypes spread

Question 12

What is a strategy to defeat the constant evolution of bacteria?

Answer 12

Give different antibiotics to different patients to slow down the transmission of bacteria between them

Question 13

What are homologous structures that humans have with primates?

Answer 13

feet and skulls, coccyx and tails

Question 14

Mass extinctions of non-avian dinosaurs triggered adaptive radiation of ___.

Answer 14

placental mammals

Question 15

The oldest primate fossils date back ___ years.

Answer 15

55 million years

Question 16

Apes and hominines are more closely related to… Old World or New World monkeys?

Answer 16

Old World monkeys

Question 17

What are the closest living relatives to humans?

Answer 17

Chimps & bonobos

Question 18

What are hominins?

Answer 18

Humans as well as all species more closely related to humans than chimps; humans are the only surviving members of the group; includes humans and all extinct species branching from human lineage after splitting from last common ancestor w/chimps

Question 19

Why are the precise relationships among hominins being debated?

Answer 19

Some species are known only from a single fossil, not even a whole skeleton; there is extensive homoplasy & some features repeatedly emerge and disappear

Question 20

What are key traits in humans that evolved over time?

Answer 20

big brains, bipedalism, tool use

Question 21

The virulence of a pathogen is influenced by what two agents of selection?

Answer 21

selection for within host replication & selection for between host transmission

Question 22

What are some consequences of antibiotic resistance?

Answer 22

• Greatly increased morbidity and mortality in humans
• Use of ineffective antibiotics delays or prolongs treatment
• No antibiotics available for some infections
• Greater health care costs
• Prolonged hospital stays
• Expensive ‘last ditch’ prescriptions
• Expensive isolation treatments
• Higher risk to health professionals

Question 23

What are features that have changed in humans from primate origins?

Answer 23

reduced prognathism (protruding jaw), brain size

Question 24

What are unique features of the Homo habilis?

Answer 24

• Orthognathic
• ECV - 770 cc
• Very large cheek teeth
• evidence of tool use, butchery
• australopithicene descendant

Question 25

What are unique features of the Homo ergaster?

Answer 25

• “working man” - used advanced tools
• fire use
• tall (6’3”)
• larger brain (850cc), small cheek teeth

Question 26

Homo ergaster is the first hominid to have what five features?

Answer 26

• Big brain (800-900 cc)
• Orthognathic
• Small cheek teeth
• Modern stature / limb proportions
• No evidence of climbing adaptations