U6 bio: evidence for evolution

what is evolution

the change in heritable characteristics of biological populations over successive generations

explain the types of hereditary change in evolution (2)

variations: are like genetic diversity within a population leading to new physical features, structures and behaviours

adaptiations:a variation that is selected via natural selection to be passed down in future generations based on its successfulness in helping indivudals survive, mate and reproduce in a specific environment

what evidences are there for evolution (6)

FC RBS

• fossils

• comparative molecular biology, anatomy and embryology

• radiometric dating

• biogeography

• selective breeding

what is a fossil and how is it produced?

what conditions make fossilization more likely

a fossil is the naturally preserved remains, impressions or traces of life found in layers of rocks or mineral deposits

they are produced through a process called permineralization

conditions that increase fossilization:

• lack of oxygen

• presence of water

• liquid that will trap the organism then solidify

• hard bodied organisms or aquatic organisms are more likely to be fossilized

what do fossils tell us about organisms and evolution?

fossils are direct evidence for microevolution → specifically gradualism

they can tell you about organisms that lived at the same time → organisms within the same strata

what is comparative molecular biology

when we compare DNA and protiens of different species to find the % of similarites or the number of differences

two organisms are presumed to have a more recent common ancestor when:

• they have high % similarity

• they have low # of differences

support for comparative molecular biology

almost all living organisms use the same 64-codon genetic code to determine what amino acids are to be placed in a particular protien

comparative anatomy:

• analogus structures

• homologus structures

• vestigial structures

analogus structures: a structure that performs the same function but has different evolutionary origins and anatomical structure

homologus structures: structures with a common evolutionary origin but have developped to have different functions

vestigial structures: a vestigial structure is an anatomical feature or behaviour that no longer seems to have a purpose in the current form of an organism

comparative embryology, what is it and what does it tell you

comparative embryology is the study of different embryos of different species, what similarities and differences exist in their early stages.

what is reveals:

• evidence of having a common ancestor: if the embryos share common features

• the more similar the embryos the more closely related the species are likely to be

radiometric dating

compares the amount of stable isotope to unstable isotope to determine how old the sample is

the unstable isotopes in the sample decay overtime to become more stable, so if there are many unstable isotopes, than that means that the sample is more modern.

biogeography

what does it tell you about evolution

definition: it is the study of the distribution of living organisms across the world

→ it shows continuos variation across a geographical area, where the populations show variation and differences from one another which matches the concept of gradualism and divergent evolution which lead to many microevolutionary changes compounding to form a macroevolutionary change (speciation)

what does this tell us about evolution:

• that organisms that are closely related are often found in the same area. these usually have a common ancestor

• species that live in similar environments but on different continents may look alike due to convergent evolution —> they evovle similar traits indpendantly

selective breeding (aka artificial selection)

is when humans choose which organisms reproduce based on desired traits

what are the theories for the creation of life (3)

creationism:

• all species of organisms were individually created exactly as they exist today

• based on creationist stories, earth is between 4000-10,000 years old

• problems: not testable, earth is 4.5 bya

panspermia:

• life didnt originate on earth and actually arrived here from space via an asteriod etc. could be intentional → directed panspermia (colonization of earth), accidental → life arrived by chance

• problems: doesnt really answer the question where life came from

abiogenesis:

• life evolved from abiotic macromolecules that came together to form the first cell like unit

explain the key steps of abiogenesis:

• Abiogensis is the theory that life originated from the synthesis of inorganic molecules from inorganic ones that eventually formed the first cell like unit (protocells which became prokaryotes)

• In order for this to happen:

  • Inorganic molecules must synthesize organic molecules 

  • Organic molecules must form polymers (ex. Amino acids → proteins)

  • Polymers must be able to self replicate (inheritance)

    • A key factor of self replication, means being able to pass on its genetic information, RNA 

    • This was done without enzymes 

  • And then membranes need to be formed around the organic molecules to finally make the cell like unit (protocells were simple cell like units which were RNA wrapped in lipid membranes)

    • Membranes needed to separate the internal environment of the organism with the external environment → compartmentalization!

    • These could be liposomes (double layered phospholipid bilayers) or micelles (single layer phospholipids)

    • Membranes allowed this first cell like unit to conduct chemical processes internally within its membrane 

    • These membranes could form in water naturally

urey miller experiment

determined that in an environment and atmospheric conditions like ancient earth, inorganic molecules can synthesize organic molecules like amino acids, sugars etc.

list the important events and times that lead to the evolution of humans

• ~4.5 billion years ago – Formation of Earth

• ~3.7 billion years ago – First chemical evidence life (single-celled organisms)

• 2 bya → eukaryotes evolved

• ~600 million years ago – First multicellular organisms

• ~500 million years ago – First vertebrates (animals with backbones)

• ~360 million years ago – Vertebrates move onto land (tetrapods)

• ~65 million years ago – Dinosaur extinction, rise of mammals

• 7–10 million years ago: Humans and chimpanzees share a common ancestor (after early primates and apes evolved

• human evolution part: hominin (bipedal hominins) → homo (genus) → first homosapiens appear in africa → migrate out of africa → neanderthals and humans coexist, but they get absorbed and outcompeted → homo sapiens remain

what compound can date up to 50,000 years? what compound can date after that?

up to 50,000 years: carbon 14

after 50,000 years: uranium-238

darwins observations (4)

1. individuals in a species vary in traits (genetic diversity)

2. some variations in traits can be inherited

3. every generation produces more offspring than the environment can support → so not all offspring can survive and pass on their variations

4. populations of species tend to remain stable in size

darwins inferences (3)

1. members of the same species must comepte with each other for survival

2. indivudals with more favourable variations are more likely to survive and pass on their genes → this means survival is not random!!

3. natural selection increases the allele frequency of favourable traits in succeeding generations

the theory of evolution by natural selection

natural selection increases the frequency of characteristics that make individuals better adapted to survival and reproduction and decreases the frequency of other characteristics (that may not be as beneficial) leading to changes within the species!

→ btw if its changes within the species thats microevolution

name 3 examples of extreme cases of natural selection

mimicry: an animal adopts the traits of another organism to increase survival (ex monarchs and viceroy butterflies)

camoflage: adapts to have the same appearance as their environment

melanism: development of dark pigment in the skin or fur → for example indsutrial melanism where moths became darker to blend in better with the trees

What were the contributions of Redi and Pasteur in disproving spontaneous generation?

• They used broth which was boiled (to eliminate any microorganism growth) and tested to see if the outside environment was the cause of growth. In the case where the external environment could not enter the broth because of the swan neck, there was no growth. However without the swan neck, the microbes from the environment would enter and cause growth. 

• It was determined that cells can only come from pre-existing cells under current conditions → supports cell theory

what are the conditions for life to arise

where did life msot likely originate

conditions:

• abiotic self replicating macromolecules (rna)

• source of energy: solar, thermal, chemical

• aquatic environment

mechanisms of DNA change

• Meiosis

• Mutations 

• Viruses 

What are Lamarck’s two laws, and why are they incorrect?

• Law of use and disuse: a trait will develop if used and disappear if unused

  • Not true, blind people don't lose their eyes 

• Law of inheritance of acquired characteristics: features and traits developed across an organism's lifespan will be passed on to subsequent generations

  • Incorrect because developed features and traits are not part of your chromosomes (genetic coding) that can be passed on through your gametes

what era did humans first appear in?

cenozoic era

long periods of speciation and macroevolution are punctuated by what?

periods of extinction

what are the 5 major extinction events

1. ordovician silurim extinction events

   • mountains absorbed CO2

   • less CO2 = cold ice age

2. devonian extinction:

   • plants gre roots, releasing nutrients into the ocean = increased algae blooms = killed ocean life

3. permoan-triassic extinction:

   • growth of membrane producing bacteria which released methane and co2 into air

   • caused warming and reduced oxygen in oceans

4. Triassic-Jurassic extinction:

   • increased temperatures and sea level

   • high CO2 levels

5. ordovician silurim extinction event:

   • meteor/asteriod

   • increased volcanic activity

what are the major evolutionary milestones for the evolution of humans

Species	Time Period	Key Features
Australopithecus afarensis	~3.9–2.9 million years ago	Walked upright (bipedal), small brain
Homo habilis	~2.4–1.4 mya	"Handy man" – used simple tools
Homo erectus	~1.9 mya – 143,000 years ago	Controlled fire, more advanced tools, migrated out of Africa
Homo neanderthalensis	~400,000 – 40,000 years ago	Lived in Europe/Asia, robust build, culture, buried dead
Homo sapiens	~300,000 years ago – present	Complex language, symbolic thinking, global migration

explain the taxonomic order of humans (homonids)

kingdom: animals

phylum: chordates

class: mammals

order: primates

family: homonids

genus: homo

species: homo sapiens

what are the most convincing evidences for evolution (3) to find a speciation pattern

comparative molecular biology (compares genomes)

biochemical analysis

comparative anatomy (cranial → fossils, direct evidence of intermidates)

what differentiates humans from other members in its taxonomic family? (great apes otherwise known as hominids)

other members of the family of homonids are:

• gorillas

• chips

• organutans

• humans

all of these species originate from a common ancestral primate. humans are most closely related to chimps (99% similarity)

we can find this pattern of speciation via comparative molecular biology and biochemical analysis

humans differ from the rest of their family because of their genome and chromosome 2:

• chromosome 2 fused together to form a singular chromosome, forming a loci where 2 chromosomes used to be separated → this gives us our 1% difference in chromosome bands

• another difference is how all apes have 48 chromosomes except for humans with 46

key changes in humans evolution over time (5)

Key Changes Over Time

• 🧠 Brain Size increased — linked to tool use, problem solving, and social behavior.

• 🚶‍♂ Bipedalism — walking upright freed hands for tool use and carrying.

• 🛠 Tool Use — improved survival, hunting, and communication.

• 🔥 Control of Fire — allowed cooking, warmth, and protection.

• 🗣 Language and Culture — development of communication, art, and societies.