BISC 102 Midterm Prep

Theory

An explanation of the natural world that has been extensively tested and supported by observation and experiment (not falsified)

T/F: Theories are open to change and even being discarded in light of new evidence?

T/F: True

Life

Carbon based cellular structures with controlled energy conversion (Metabolism), ability to replicate, store and process information, with variations, able to evolve

Louis Pasteur

This person tested which hypothesis about life was correct: spontaneous generation or all cells from cells

Pasteur’s experiment

Set up flasks, one with a flask that doesn’t allow cells in and one that does. This experiment supported the hypothesis that all cells come from existing cells

Panspermia hypothesis

“All seeding” Life originated elsewhere in the universe, and was “seeded” on Earth from space from (comets, asteroids or other cosmic source)

T/F: Was the panspermia hypothesis a crackpot theory?

T/F: no, seeding of complex biomolecules such as amino acids has been proposed, raw materials for life to form?

T/F: amino acids occur in space

T/F: True, amino acids have been found in comets, interstellar dust clouds and carbonaceous meteorites

Other hypothesis for life on Earth

Amino acids are easy on Earth (Stanley L. Miller and Harold Urey classic Life Spark Experiment)

What are Origin of Life experiments?

Biochemistry (Chemical evolution), not biological evolution, which begins with the first population of living organisms

LUCA “Last Universal Common Ancestor” (Theoretical) of Life

Unknown most recent common ancestor of all current life on Earth (not necessarily the first life form, but the first surviving one): basic genes shared by 3 domains

Where did LUCA likely form?

Hydrothermal vents, where energy, raw materials, and other key condition are present in seawater (likely but not confirmed)

What follows the survival of LUCA is what Charles Darwin called ____

Descent with modification, now known as biological evolution

What was LUCA probably the ancestor of?

Archaea (rather than true bacteria)

Until the 1970s, life was classified into 5 kingdoms, which were

bacteria, animals, plants, fungi and protists

Biochemical research, including DNA, confirmed that although both archaea and bacteria are unicellular prokaryotes and look alike, they are fundamentally____

different in their biochemistry (cell wall and membrane composition), and other features

Unicellular prokaryote

no nucleii or organelles

Archaea are called ____: found in extreme environments like hot springs and animal guts

“extremophiles”

Universal Tree of Life

A continually updated phylogeny of the 3 domains of life, based on genetic sequencing of ribosomal RNA, an ancient form of RNA that all life forms in the 3 domains share

Eukaryotes

have larger, more complex cells than prokaryotes, with membrane bound nucleii and organelles, but also have ribosomes (rRNA) inside cells. Animals, fungi and land plants are the most common Eukaryotes seen by humans

What are Eukaryotes more closely related to?

Eukaryotes are more closely related to Archaea than bacteria, based on genetic and biochemical similarities

first evolutionary tree

1837 Darwin’s sketch from his notebook, 22 years before publishing Origin of Species in 1859

Past crossovers in the tree

Some evolution can happen by horizontal transfers of DNA or whole organisms. E: Cyanobacteria gave rise to chloroplasts and proteobacteria are ancestral to mitochondria

Taxonomy

system of classification of organisms

Binomial naming system

Linnaean, all organisms given a binomial name in Latin, comprised of Genus followed by a species name

Alexander von Humbolt

German scientists, naturalist and geographer that has more things named after him than anyone else

Central Dogma of Biology

Based on the discovery of the structure and function of the DNA double helix by Watson and Crick (And Rosaline Franklin and Maurice Wilkins)

Who made the first accepted correct model of the double helix of DNA?

Watson and Crick in 1953

Evolution

The change in the genetic characteristics of a population over time.

Population

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

T/F: Individuals within a population can evolve

T/F: False, they may live or die, reproduce or not, but only the population can evolve

T/F: Darwin used the word evolution

T/F: False, he used the term descent with modification, for his view of change in organisms, derived from both artificial selection of variations in domesticated animals and plants, and his insight of natural selection in nature

Microevolution today

Microorganisms evolve most rapidly, especially viruses. Covid variants and subvariants like Omicron and Kraken are current examples. Mutations alter spike proteins, changing the ability of mutants to attach to host cells.

On the Origin of Species

Focused on natural selection as the key process of biological change over time

Whose key insights form a foundation of modern evolution today?

Charles Darwin

What are Darwin’s 2 key insights?

Explained how biodiversity came to be a mechanism, documented many examples from both natural and artificial selection

First of Darwin’s key insights

Explained how biodiversity came to be: a mechanism, natural selection acting on a variation. (Although he knew nothing of chromosomes, genes, DNA or other sources of heredity, only that traits are somehow passed from parents to offspring

Second of Darwin’s 2 Key Insights

Documented many examples from both natural and artificial selection that plants and animals are products of descent with modification from ancestral forms.

Ideas before Darwin

Most Classical philosophers and scholars were creationists (Believed that a deity created the universe and all life forms by supernatural means), but some were curious about the natural world

Ancient World: Greece and Rome

Emphasis on mythology, supernatural stories and strange combinations of living things. But some philosophers tries to make sense of nature through careful observations of real organisms

Plato

Greek philosopher Plato claimed that every organism was an example of a perfect essence or type created by god and these types were unchanging

Typological thinking

Every organism thought to be an example of a perfect essence or type created by god and that these types were unchanging. Variations in these species were unimportant noise to understanding origin

Aristotle

Greek philosopher ordered known organisms into the linear great chain of being

Scale of Nature

Linear great chain of being in which species were fixed types, species were organized into a sequence based on size and complexity, sequence started with minerals and lower plants, and humans were at the top of the chain

T/F: Enlightenment was the age of reason

T/F: True, Enlightenment = age of reason

Early hints about changes in nature

Earth formed according to laws of physics and chemistry, older than previously thought, and life emerged as distinct species that could transform when the environment changed

When was the age of reason?

1600-1700s AD

Who proposed the first (but flawed) evolutionary theory (beginning with continual spontaneous generation)?

Jean Baptiste Lamark

What was believed in the Enlightenment?

Life emerged as distinct types that could change when the environment changed and that the earth is formed according to the laws of physics

T/F: Natural selection uses population thinking rather than individual thinking

T/F: true, it uses population thinking

Who claimed that inherited variations among individuals in a population are key to understanding evolution?

Darwin and Wallace

Paleontology

Study of fossils

What had a profound impact on early evolutionary thinking?

Fossils and Paleontology

What fossil was a clear intermediate between reptiles and birds?

the Archaeopteryx

Georges Cuvier

In Paris, fossils resemble but are not exactly the same as modern species. Extinctions are a fact! Very controversial with creationists

Darwin’s timeline

Grew up in Shrewsbury, England in an upper class medial family, then medical school in Edinburgh, trained to become a clergyman at Cambridge, then invited to serve as a unofficial naturalist and gentleman companion

Context for Darwin’s thinking

Aristotle’s great chain of being was still generally accepted and that earth was still very young, and that landforms were fixed

Main purpose of the Beagle voyage

To map the coast of South Africa and voyage around the world making latitude and longitude measurements

How long was the voyage of the Beagle?

5 years, meant to be 2

What did Darwin read?

Principles of Geology by Charles Lyell, and concluded that supernatural processes weren’t needed as explanations for natural processes observed today

What did Darwin find on the Galapagos islands?

A great number of aboriginal creations (endemic species only found there), variation of the same species across the islands, gradation and diversity among birds, and similarities to South American species

Phylogenetic tree

diagram that illustrates the ancestor-descendant relationship among taxa. Illustration of a hypothesis about the ancestor-descendant relationships among taxa based on currently available information. They’re grouped into phylogenetic taxa based on unique shared traits that result from common ancestry.

T/F: Galapagos mockingbirds do not share a common ancestor and are not each others’ closest living relatives

T/F: False, they are in fact each other’s closest living relatives and share a common ancestor

Endemic

A species native and restricted to a certain place

Why did Darwin not release his findings for decades?

He was worried about the social impact of his findings in Victorian England

Who was Darwin’s Bulldog?

Thomos H. Huxley, a biologist

Who was the forgotten evolutionary thinker?

Alfred Russel Wallace was

What did Alfred Wallace find?

Found similar evolutionary ideas as Darwin, found in Malayan region: common ancestry of life forms, natural selection changes species, but lost main collections in ship fire.

What prompted Darwin to publish his theory?

Huxley

When was Darwin’s Most famous book published?

On the origin of species by means of natural selection, or the preservation of favored races in the struggle for life was published in 1859

What did Darwin’s book have in it?

Descent with modification, all species share common ancestry, heritable variations present in all organisms, changes occur through natural selection

Darwin’s 4 Postulates were

Individual variation, inheritance, overproduction, competition

Observation 1 of Darwin’s 4 postulates

Individual variation - individuals within a species vary in traits and characteristics

Observation 2 of Darwin’s 4 postulates

Inheritance, traits are inherited by offspring from their parents

Observation 3 of Darwin’s 4 postulates

overproduction, more individuals are born than can survive in a stable population

Observation 4 of Darwin’s postulates

Competition, individuals compete for resources

Genotypes

Genetic composition of an individual organism’s DNA

Phenotypes

physical expression of the genotype, often referred to as the physical characteristics or traits

Natural selection

Process that sorts the phenotypes of a population (any by proxy also sorts the underlying genotypes

Natural selection: textbook focus

The process by which individuals with certain heritable traits tend to produce more surviving offspring than individuals without those traits, leading to a change in the genetic makeup of the population

T/F; Natural selection can act as any heritable trait (i.e a characteristic based on genetic variation)

T/f: True, it can

Phenotype differences are?

Physical structural differences, physiological and biochemical differences, developmental patterns

Physical or structural differences

body or body part size, shapes, colors, patterns

Physiological and biochemical differences

proteins, structural and regulatory, enzymes and hormones

T/F: traits can also include any genetic differences

T/F: true, DNA changes as small as single nucleotide differences (point mutations), or different DNA sequences, small or large

Conditions for natural selection

There is a heritable (genetic) variation, the variation results in a fitness differential (=advantage or disadvantage to reproduction in the current environment), then that trait will evolve in that population by natural selection

Evolutionary fitness

Not survival alone, but an individual’s contribution of genes to the next generation (i.e reproductive success compared to others)

Physical fitness

Good health or physically in good shape. But not evolutionary fit if no children produced

What determines evolutionary fitness?

number of surviving offspring produced to the next generation (population gene pool)

What was key evidence for Darwin?

Enormous variability potential in species, artificial selection was key evidence for Darwin

Homologous traits

similar structures in descendent organisms can be explained as a result from inheritance from a common ancestor

Homology examples

vertebrates having 4 limbs

Homoplasy

Convergent evolution, a trait that has evolved independently in two different species or organisms not because of a common ancestor

What evidence for the evolution of cetaceans, whales and dolphins, illustrate the idea of internal consistency?

Fossil cetaceans have unique ear bones only found in living and fossil cetaceans, skeletons of fossil cetaceans indicate transitions between terrestrial, amphibious and aquatic forms, vestigial hip and limb bones are found in some living and fossil adult whales and in dolphin embryos

How are vestigial structures evidence for evolution?

provide evidence for common ancestry, ex: whales have a vestigial hip and limb bones. The genetic information to make hind limbs is still there, but has been stopped at some point due to genetic regulation

Directional selection

Changes the average value of a trait

Stabilizing selection (also common)

Average individuals are favored, high fitness = stability. Selection against extreme traits

Before claiming natural selection, must show that

1. heritable variation exists (is beak depth a heritable trait?) - Yes, offspring inherited the larger beaks of surviving parents

2. A fitness differential exists (is there an advantage for having different beak depths?) - yes, survival and reproduction was better for birds with beaks larger than average that could crack larger seeds from drought plants

T/F: Natural selection changes individuals

T/f: False, it SORTS them

Corrections about natural selection

1. individuals can’t evolve, only populations of a species can evolve

2. Individuals do not select which genes to pass on, reproductive individuals pass on genes that may be advantageous or disadvantageous

3. Selection (not random) is adaptive, but mutations and genetic drift occur naturally

4. Natural selection is not purposeful or forward looking, but operates in the present environment

5. Evolution does not produce perfections, only workable adaptations

6. Evolution is not goal directed, adaptations don’t occur because organisms want or needs them (ex: roses have thorns because some ancestors had a thorn producing mutation, and survived and reproduced more effectively than those without thorns