evolution

Question 1

what are vestigial traits, and why are they powerful evidence for evolution?

Answer 1

vestigial traits are reduced or non-functional structure inherited from ancestors
EX: human tailbones (coccyx) python hip bones
they are strong evidence for evolution bc/ they have no function explanation without ancestry - they only make sense in light of evolutionary history

Question 2

what limits evolutionary outcomes even when selection is strong?

Answer 2

genetic constraints > the available genetic variation in a population limits what traits can evolve. Evolution can only work with existing variation; it cannot produce traits for which no heritable variation exists. this is why evolution does not produce perfect adaptations

Question 3

what is evolution?

Answer 3

1. Pattern: living species are descendants of ancestral species that were different from present-day ones
2. process: the change in the genetic composition of a population from generation to generation

Question 4

what does it mean that evolution is both a pattern and a process?

Answer 4

pattern: evolutionary change revealed by data/facts/observations on the natural world
process: the mechanisms that produce the observed pattern > natural causes of natural phenomena

Question 5

what are adaptation and how do they relate to natural selection?

Answer 5

adaptation = inherited characteristics of an organism that enhance its survival and reproduction in a specific environment

environmental adaptation = origin of new species (Darwin’s core link)

adaptation arise via natural selection

Question 6

define natural selection

Answer 6

a process where individuals with certain heritable traits survive and reproduce at a higher rate than other individuals

overtime, increases the frequency of advantageous traits in a population
KEY: individuals don’t evolve > populations do

Question 7

what are the 2 key observations and 2 inferences of natural selection?

Answer 7

Observations:
1. members of a population vary in inherited traits
2. all species can produce more offspring than the environment can support > many fail to survive/reproduce

Inferences:
1. individuals with favorable traits leave more offspring
2. unequal ability to survive/reproduce > accumulation of favourable traits over generations

Question 8

what are the 3 KEY POINTS about natural selection?

Answer 8

1. Individuals do NOT evolve — populations do.
2. Nat. sel. can only amplify or diminish traits that differ among individuals (if a population is genetically identical for a trait, evolution by nat. sel. can’t occur).
3. Nat. sel. always operates, but which traits are favoured depends on the species’ environment.

Question 9

define homologous characteristics vs. analogous (convergent) characteristics

Answer 9

Homologous: in different organisms > similar bs/ inherited from a common ancestor

analogous (convergent): similar characteristics due to shared environmental constraints, NOT a close evolutionary relationship. Related to convergent evolution > organisms that evolve similar featured as solutions to the same problems

Question 10

what is Scala Naturae (great chain of being)?

Answer 10

the idea from Greek philosophy that organisms can be arranged on a ladder/scale of complexity from simple to complex

Aristotle thought species were fixed. supported by the Old testament > species individually designed by God > perfect

Question 11

what did Carolus Linnaeus believe and contribute?

Answer 11

developed binomial nomenclature and a nested classification system. Grouped organisms by genus

DID NOT base classification on evolutionary kinship. Darwin later argued classification SHOULD reflect evolutionary relationships

Question 12

what are strata and what is their significance?

Answer 12

Strata (stratum) = rock layers formed when new sediment covers older layers

give a glimpse of organisms living at the time they were formed. Revealed through erosion, Foundation of paleontology

Question 13

who was Georges Cuvier and what did he contribute?

Answer 13

French scientist (1769–1832) who largely developed paleontology.
Noticed: the older the strata, the less similar fossils were to current life-forms.

Proposed: across layers, some species disappeared and some appeared — explained by catastrophes wiping out populations, with new species immigrating after (sudden events). Believed in commonality of extinctions, but NOT evolution.

Question 14

how does Cuvier’s hypothesis differ from Lamarck’s? which is scientific?

Answer 14

Cuvier (catastrophism): Species don’t evolve; catastrophes cause extinctions confined to local regions, later repopulated by other species immigrating. ✗ Testable against fossil record → belief species don’t evolve = false.

Lamarck (use & disuse + inheritance of acquired characteristics): Testable in predictions for fossils as groups adapted to new habitats → inheritance of acquired chars in living organisms = false.

Both are scientific (testable).

Question 15

what is Lamarck’s hypothesis of evolution? what was he right and wrong about?

Answer 15

Recognized: Evolution explains patterns in fossils.
Remembered for incorrect mechanism:

Accepted principles:
1. Use & disuse — body parts often used → bigger, stronger; not used → deteriorate.
2. Inheritance of acquired characteristics — parents pass down developed characteristics to offspring (Darwin also believed this — eg. mother who dyes her hair will pass that hair colour to offspring). ✗

Also believed organisms had an innate drive to become more complex → Darwin rejected this.

Question 16

what were the key details and finding of the Voyage of the Beagle?

Answer 16

Aimed to chart poorly-known stretches of South American coast.

Findings:
* Organisms from temperate regions of SA more similar to SA tropics than to temperate Europe.
* Fossils differed from, but resembled, living organisms of SA.
* Galápagos: birds were similar but different species; some unique to islands, others on adjacent islands.
* Galápagos animals resembled SA species but not found anywhere else world-wide.

Hypothesized: SA organisms → Galápagos → diversified, giving rise to new species on various islands

Question 17

what is the key example of adaptation from the Galapagos finches?

Answer 17

Galápagos finches = beaks & behaviour adapted to specific foods on different islands.

The most recent common ancestor was an insect-eating finch; not all descendants are insect-eaters.
Used as evidence for adaptive radiation from a mainland ancestor.

Question 18

What is artificial selection, and how did it influence Darwin’s thinking?

Answer 18

Selective breeding (eg. domesticated plants and animals) — selecting & breeding individuals with desired traits → results in crops, livestock, pets that have little resemblance to wild ancestors (artificial selection).

Led Darwin to believe a similar process occurs in nature, based on 2 observations about populations.

Question 19

How did Malthus influence Darwin’s theory of natural selection?

Answer 19

Malthus: human suffering (disease, famine, war) results from human pop. inc. faster than food/resources.

→ Traits advantageous for survival & reproduction are favoured → appear at greater frequency next gen.
→ Over time, most individuals will possess the favourable traits → refines match of organism to environment.

Question 20

Ideas from The Origin of Species — what does descent w/ modification by nat. sel. explain?

Answer 20

Explains:
* Unity of life → organisms share many characteristics.
* Diversity of life.
* Match between organisms and their environments.

Also: extinction and the branching concept explain why there may be morphological gaps between related species (can document divergence or present-day groups by ‘filling in’ gaps between them).

Question 21

What links common ancestry to diversity of life?

Answer 21

Descent with Modification → unity AND diversity of life.

• Common ancestors → diversify as populations move and adapt to their different, respective environments.

Homologous characteristics: In different organisms that are similar bc they were inherited from a common ancestor.
Analogous (convergent): Similar characteristics due to shared environmental constraints, NOT a close evolutionary relationship — related to convergent evolution.

Question 22

What are the 4 types of evidence for evolution?

Answer 22

1. Direct observations of evolution (eg. beak length depending on seed depth, south vs central Pt bugs)
2. Homology
3. The fossil record
4. Biogeography

Question 23

What is the MRSA case study, and what does it illustrate about natural selection?

Answer 23

Principles highlighted: Nat. sel. edits existing traits rather than creating new ones; rapid evolution occurs in species with short generation times; nat. sel. is context-dependent.

Question 24

What is Homology and what does it refer to?

Answer 24

Refers to similarities resulting from common ancestry.

Evolution = as a process of descent w/ modification, alters ancestral traits in descendants, resulting in shared structures that may serve different functions.

Question 25

What are molecular homologies?

Answer 25

All life shares a universal genetic code, indicating descent from a common ancestor. Homologous genes exist across diverse species, retaining original function (eg. ribosomal genes) or acquiring new functions. Some species have inactive 'pseudogenes' reflecting shared evolutionary history.

Question 26

What is the nested pattern of homologies?

Answer 26

Homologies form a nested pattern, reflecting descent w/ modification: → Broad traits (eg. backbones) are shared by larger groups (eg. all vertebrates). → Specific traits (eg. amnion, feathers) are shared by smaller groups within the larger set. Deeply ancestral homologies (eg. genetic code) = shared across ALL species. Recent homologies = shared only within smaller, more closely related groups (eg. tetrapods have limbs w/ digits).

Question 27

What is convergent evolution? How does it differ from homology?

Answer 27

The independent evolution of similar features in different evolutionary lineages due to adaptation to similar environments. → Leads to analogous features: those with similar functions but NOT common ancestry. Homologous features = shared ancestry, but not necessarily similar function (eg. mammalian forelimbs). Analogous features = similar features that evolved independently (eg. sugar glider and flying squirrel gliding adaptations). → Convergent evolution illustrates how similar environmental pressures can shape similar adaptations in unrelated species.

Question 28

What are evolutionary trees, and what is 'tree thinking'?

Answer 28

Evolutionary trees represent relationships among species, showing how groups descend from common ancestors. Branch points signify the most recent common ancestor of descendant species. Tree thinking: Closer placement on the tree doesn't necessarily mean closer evolutionary relationships — relationships depend on the most recent common ancestor. eg. Mammals and birds are more closely related to each other than to amphibians, as they share a more recent common ancestor.

Question 29

What is the fossil record's role as evidence for evolution?

Answer 29

Role of fossils: * Reveal that past organisms were different from present-day species and many have gone extinct. * Show evolutionary changes within groups and emergence of new traits (eg. reduction of pelvic bones in fossil stickleback fish, driven by nat. sel.).

Question 30

What is biogeography and what evidence does it provide for evolution?

Answer 30

Study of the geographic distribution of species and how these patterns provide evidence for evolution. Significance: Biogeographic patterns reflect evolutionary processes and provide evidence for common ancestry, adaptation, and the role of geography in shaping species distribution.

Question 31

What does it mean that evolution is a 'theory' in science?

Answer 31

In science, a theory = a comprehensive explanation supported by substantial evidence — NOT a mere hypothesis or guess. The theory of evolution by natural selection integrates and explains a wide range of observations and phenomena. Scientific theories are rigorously tested and updated: → Evolution is not always slow; speciation can occur rapidly (eg. within thousands of years). → Nat. sel. is NOT the sole evolutionary mechanism; other processes (eg. genetic drift) also play a role.

Question 32

What is the broader significance of evolution?

Answer 32

Evolution explains the unity and diversity of life, linking all living organisms to a shared ancestry. The study of evolution is dynamic, incorporating experimental approaches and genetic analyses to refine our understanding.

Question 33

What are pseudogenes and why do they support evolution?

Answer 33

Pseudogenes = inactive 'pseudogenes' found in some species. Reflect shared evolutionary history — molecular homologies indicating descent from a common ancestor.

Question 34

Divergence despite similar environments — what does it show?

Answer 34

Two islands with similar climates and habitats but in different parts of the world are populated by species related to their nearby mainland rather than each other. Supports the idea of descent with modification and geographic influence over evolutionary pathways.

Question 35

Why is 'survival of the fittest' a misleading description of natural selection?

Answer 35

'Fittest' implies physical strength, but in evolutionary biology fitness = reproductive success. An organism can be small and weak but highly fit if it produces many surviving offspring. The phrase also implies a competition when natural selection is really about differential reproduction.

Question 36

What is convergent evolution, and how does it differ from homology?

Answer 36

Convergent evolution is the independent evolution of similar traits in unrelated lineages, driven by similar selective pressures. The resulting traits are analogous (similar function, different origin), NOT homologous. Example: wings in birds, bats, and insects evolved independently — structurally very different.

Question 37

What are the three domains of life, and how were they established?

Answer 37

Bacteria, Archaea, and Eukarya. Established through analysis of ribosomal RNA sequences across all living organisms — molecular evidence revealed that Archaea are as distinct from Bacteria as either is from Eukarya.

Question 38

What is Evo-Devo, and what does it reveal about evolution?

Answer 38

Evolutionary developmental biology (Evo-Devo) studies how development reveals ancestry. All vertebrate embryos have tails and pharyngeal arches — these become gills in fish but ear and throat structures in mammals, showing deep shared ancestry.

Question 39

Define fitness, phenotypic selection, and heritability.

Answer 39

Fitness = reproductive success (number of offspring that survive and reproduce). Phenotypic selection = differential survival and reproduction based on traits. Heritability = the degree to which a trait resembles parents in offspring — the mechanism by which selection leads to evolutionary change.