BIO94 - QUIZ 4

What are key adaptations of primates for tree-living

• Grasping hands & feet

• Forward-facing eyes (depth perception)

• Large brain relative to body size

• Flexible limbs & shoulder joints

How are humans related to other primates?

• Humans share a common ancestor with chimp (~6-7 mya).

• similarity with chimps is ~95-99%.

• Humans belong to the family Hominidae (great apes) and the subfamily Homininae.

What is the difference between Hominid and Hominin?

Hominid: Includes all great apes (gorillas, chimps, humans). extended

Hominin: Humans & extinct relatives after split from chimp. immediate

What are the two major hominin genera?

Australopithecus (5 - 2.2 mya): First bipedal (walk upright) hominins.

Homo (2.3 mya - present): Larger brain, tool use, migration.

What was the first major hominin innovation?

• Bipedalism (walking on two legs)

• Adaptation to savanna environments as forests shrank

Who was “Lucy” (Australopithecus afarensis)?

Lived ~3.7-3 mya

“Ape brain, human body”

Small groups, upright walker, long arms for climbing. show evolution

What major changes did Homo habilis introduce?

habilis (handy) First known tool-maker (“handy man”).

Larger brain & smaller jaw than Australopithecus.

Lived in larger groups, improving social skills.

Homo habilis as early human starting to use tool, bigger brain

What adaptations made Homo erectus successful?

• First species to leave Africa (~1.8 mya)

• Taller, better adapted for long-distance walking & running

• Used fire & complex tools

• Broad, flexible diet (may have cooked food).

• erectus: upright

What is the “Out of Africa 1” migration?

• Homo erectus spread from Africa to Asia & Europe (~1.8 mya).

• multi-purpose hand axes

• Lived in caves, adapted to temperate climates.

Who were the Neanderthals (Homo neanderthalensis)?

• Lived ~500kya - 25kya (Europe & western Asia).

• Stocky, strong, cold-adapted.

• Used tools, possibly had language & culture.

Did Neanderthals contribute to modern human DNA?

Yes, interbred with Homo sapiens.

Modern non-African humans have ~1-2% Neanderthal DNA.

What is the “Out of Africa 2” hypothesis?

• Homo sapiens evolved in Africa (~300kya) & migrated globally (~50-60kya).

• Fossil & genetic evidence supports African origins.

What is a haplotype?

A set of genetic markers inherited together.

What is “Mitochondrial Eve” & “Y-Chromosome Adam”?

mtDNA Eve: Common maternal ancestor (~200-150kya, Africa).

Y-MRCA: Common paternal ancestor (~150-250kya, Africa).

They did not live at the same time or place.

How does mtDNA & Y-DNA help trace human migrations?

mtDNA (from mothers) and Y-DNA (from fathers) reveal ancient migration patterns.

Shows genetic bottleneck events (~60-75kya).

What are the major takeaways from human evolution?

Australopithecus → Homo habilis → Homo erectus → Homo sapiens.

Bipedalism evolved first, followed by larger brains & tool-making.

Homo sapiens originated in Africa & later migrated globally.

DNA evidence confirms human evolution & interbreeding with Neanderthals.

What are the key traits that define primates?

Grasping hands and feet

Large brains relative to body size

Forward-facing eyes (depth perception)

Flattened nails instead of claws

Extended parental care

Complex social behavior

What distinguishes humans from other primates?

Bipedalism (walking upright on two legs)

Larger brains (relative to body size)

Complex tool use and culture

Advanced language and symbolic thought

Reduced body hair

What is a population in ecological terms?

group of individuals of the same species living in the same area at the same time.

key factors affecting population growth?

Birth rate (b), Death rate (d), Immigration, and Emigration.

(Simplified: Population grows when b + immigration > d + emigration.)

Define per capita rate of increase (r).

r=b−d. It represents the instantaneous growth rate of a population.

r>0 population growing

r<0 population declining

What happens when r = 0?

The population size remains constant (zero population growth)

What is exponential growth?

Population increases rapidly and indefinitely when 𝑟 is positive and constant.

Why does the number of individuals added each generation increase even if

𝑟 is constant?

Because the population size (𝑁) keeps increasing, leading to more individuals being born each time.

Can exponential growth continue indefinitely? Why or why not?

No. Resources (food, space) are limited, leading to competition and environmental resistance

What is logistic growth?

A model where population growth slows as it reaches carrying capacity (K) due to limited resources.

What happens when a population exceeds carrying capacity (K)?

Overcrowding, increased death rates, and resource depletion may cause the population to decline.

Why do life tables only include females?

Because females determine reproductive output in most species.

What are the three types of survivorship curves?

Type I – High survival early/mid-life, declines in old age (e.g., humans).

Type II – Constant death rate (e.g., birds).

Type III – High early mortality, but survivors live long (e.g., fish, trees).

What type of survivorship curve do humans follow?

Type I, as survival is high in early and mid-life but drops in old age.

How has human population growth differed from other species?

Humans have experienced exponential growth due to advancements in medicine, agriculture, and technology.

What factors contribute to density-dependent regulation of human populations?

Food supply, disease, competition, predation, and waste accumulation.

What is the demographic transition model?

A model describing how human populations shift from high birth/death rates to low birth/death rates with industrialization.

Why do conservationists study population ecology?

To manage endangered species, control invasive species, and ensure sustainable resource use.

What is the Allee effect?

A situation where populations decline at low densities due to difficulty finding mates, social cooperation, etc.

What happens when a population experiences overharvesting?

Declines in genetic diversity and possible extinction.

How did early humans survive during the hunter-gatherer era?

They were hunters and gatherers, radiated widely, made advanced tools, hunted cooperatively, and had low birth rates.

What describes population growth during this period?

Growth was slow due to low birth rates and high mortality.

What key changes occurred with the Agricultural Revolution?

Early settlements formed, labor specialization increased, food production rose, and reproductive rates increased.

How did population growth change?

Inter-birth intervals decreased (from 4-5 years to <2 years), leading to faster population growth.

What were the downsides of early agriculture?

Cramped living conditions, increased disease transmission (zoonoses), and diet narrowing.

How did the Scientific & Industrial Revolutions impact human population growth?

Improved sanitation, better water supply, and medical advances led to decreased mortality despite continued disease outbreaks.

What was a major pandemic during this time? Scientific & Industrial Revolution (~1850 - Present)

The H1N1 (1918-1920) flu epidemic, which killed 5% of the world’s population.

What major medical advances occurred from 1940s-60s?

The antibiotic revolution, coinciding with the peak of global births (Baby Boom, 5.0 births per female).

What innovations emerged in the 1970s and 1980s

Genetically modified organisms (GMOs) (e.g., golden rice for vitamin A).

Biotechnology-based drugs (e.g., human insulin from bacteria).

What is carrying capacity (K)?

The number of organisms an environment can support.

How have revolutions affected K?

Three major revolutions increased K, but sustainable population size is uncertain.

What factor strongly influences lower birth rates?

Female literacy.

How does resource use vary globally?

One person in the U.S. consumes 20x more resources than someone in a less developed country (LDC).

What are two major environmental consequences of human population growth?

Global Climate Change (increasing CO2, burning fossil fuels, deforestation).

6th Mass Extinction (habitat destruction, invasive species, pollution, climate change).

Homo sapiens origin

Evolved in Africa and shares a common ancestor with bonobos. Did not evolve from chimpanzees but from a shared ancestor.

Out of Africa 2 Hypothesis supporting fossil

Homo sapiens idaltu – an early human fossil supporting the idea that modern humans came from Africa and spread worldwide.

Neanderthals and Homo sapiens

Neanderthals were a separate species but interbred with humans. DNA shows some Neanderthal genes in modern humans.

Homo ergaster & Homo erectus

Early human species that spread from Africa, adapted to new places, and evolved into different human-like species.

Multiregional vs. Out of Africa Hypothesis

➡ Multiregional: Humans evolved in different regions with gene mixing.

➡ Out of Africa: Modern humans evolved in Africa and replaced older human species.

Three revolutions that grew human populations

➡ Agricultural Revolution (~10,000 years ago): Farming allowed food surplus, settlements, and bigger families.

➡ Industrial Revolution (~160 years ago): Machines, better sanitation, and urban growth increased population.

➡ Medical & Biotechnology Revolution (1950s - now): Antibiotics, vaccines, and healthcare improvements helped more people survive.

Age pyramid & population growth

A wider base (more young people) means faster growth. A narrow or even shape means slow or no growth.