Earth's Formation and Early Conditions

Earth's Formation and Early Conditions

• Earth formed approximately 4.6 billion years ago, as part of the solar system
• Solar system formation occurred via the nebular hypothesis
• According to this hypothesis, a solar nebula, a giant rotating cloud of gas and dust, gave rise to the solar system
• An unknown event, like a supernova shockwave, triggered the cloud's collapse under gravity
• The collapsing gas cloud formed a flat, rotating disk
• The center's increasing gravitational pull drew in more material
• Around 99.8% of the material formed a giant gas and dust ball at the disk's center
• Accumulating matter caused intense pressure and heat, leading to hydrogen fusion and helium creation
• This process birthed the sun

Planet Formation

• Material remained after the sun's formation and continued to revolve around it
• Gravity caused this material to coalesce, with small rocks forming larger ones
• These rocks formed planetesimals, which collided to create planets
• Smaller clumps of material became dwarf planets, moons, asteroids, and comets through accretion
• Collisions led some dwarf planets to grow into the solar system's eight planets, including Earth

Early Earth

• Discovering early Earth's exact conditions poses a challenge for scientists
• Early Earth was likely molten, then very hot with many volcanoes
• Asteroid collisions frequently cratered and heated the surface
• Volcanoes emitted lava and gases, contributing to the formation of a new atmosphere
• Cooling led to the formation of a solid rock surface, offering clues to early Earth's nature

Earth's Uniqueness and Conditions for Life

• Earths position, size, and composition have influenced the formation and evolution of life
• Earth is unique as the only known planet to support life, partially due to its distance from the sun
• Objects too close receive too much solar energy, while those too far receive too little
• The habitable zone is the optimal distance for life to thrive

Atmosphere and Liquid Water

• An atmosphere and its distance from the sun help maintain an average surface air temperature of 15°C
• The atmosphere comprises of nitrogen, oxygen, carbon dioxide, and water vapor
• It retains heavier gases due to its mass and gravitational force, but lighter gases escape
• A protective ozone layer shields life from harmful ultraviolet radiation
• A magnetic field protects the atmosphere from solar winds
• Convective motion of liquid metal in the outer core generates the magnetic field, sustaining life

Significance of Water

• Water is essential for life as water can exist in solid, liquid, and gas states due to Earth's moderate temperatures
• Oceans consist of liquid water, while the atmosphere contains water vapor
• Earth's weather occurs in the atmosphere, facilitating the movement of water and air
• The water cycle involves all forms of water

Origin and Evidence of Life

• Life on Earth originated around 3.5 billion years ago
• Microfossils, and stromatolites provide early evidence of life
• Some scientists propose life began near seafloor hydrothermal vents
• DNA is used by all life to pass on information from one generation to the next
• All life is related and scientists have traced the most likely common ancestor of all life to a microbe

Fossils

• Fossils preserve evidence of once-living organisms
• Body fossils include shells, bones, and teeth
• Trace fossils come from organism activities and include feces, footprints, or burrows
• Fossils are found in sedimentary rocks and exist from microscopic bacteria to giant trees and dinosaurs

Fossil Formation and Types

• Rapid sediment settlement creates ideal fossil formation and preservation conditions as rapid burial protects from decay and scavengers
• Fossilization happens in various ways
• Organisms can be preserved in ice, amber, or tar
• Molds create detailed imprints in rock
• Casts form when minerals fill molds
• Carbonized fossils leave a thin carbon film
• Replacement fossils involve mineral replacement of original material

Limitations and Interpretation of the Fossil Record

• Fossils cannot provide a complete record of an organism's appearance as fossilization is rare and incomplete
• Hard parts are more commonly preserved
• The fossil record aids scientists to interpret life on Earth, despite missing pieces
• Rock layers and fossil order help determine relative ages
• Relative dating compares fossil ages
• Absolute dating uses radioactive elements to estimate rock age ranges and works best on igneous rocks

Dating Methods

• Combining absolute dating and fossil types help create a geological time scale
• Index fossils identify rock age
• Fossil age and organism order provide information on inter-species relationships
• All life originated from one event and organisms can be related
• Relating relative ages helps build family relationship

Patterns in the Fossil Record

• Species occupy specific time intervals
• Fossil species differ from modern species
• Species appear, diversify, and disappear
• Extinction occurs, with only a fraction of past species existing today
• Extinction can be caused by competition or environmental changes

Mass Extinctions and Adaptive Radiation

• The fossil record reveals patterns of mass extinctions
• Mass extinctions are linked to asteroid impacts, volcanic eruptions, methane releases, and climate change
• The largest mass extinction wiped out 96% of species 250 million years ago
• An asteroid impact caused the extinction 66-65 million years ago that wiped out the dinosaurs
• Adaptive radiation is the rise in species diversification after a mass extinction
• Adaptive radiation happens when a trait allows survival in a habitat or enables competition

Evolutionary Trees and Transitional Forms

• New fossil species show evolution over time
• Fossil species characteristics help build family trees
• Nodes signify common ancestors
• Evolutionary trees help predict common ancestor existence
• Scientists use fossil and rock age to search for transitional forms, combining fossil data with other information to generate evolutionary trees

Contrasting Ancient and Modern Organisms

• Examining current organisms and fossil records reveals trends
• Fossils similar to modern species are discovered
• More recent fossils closely resemble extant forms
• Arthropods from millions of years ago had features in common with modern ones
• Fossil organisms in similar ecological role occupy similar ecological niches

Fossil Behavior and Diet

• Fossils provide data on extinct organism structure
• Fossil structures can be compared with modern organisms to infer aspects of their behavior
• Analysis of animal teeth reveals microscopic wear
• The "Lucy" fossil shows tough grasses and leaves were her diet
• Fossilized stomach contents shed insight on diet
• Analysis of fossilized feces reveal ecosystem feeding relationships

Interpreting Ancient Ecosystems

• Understanding ancient ecosystems involves studying fossils together, which helps scientists interpret groups of fossils related to warm saltwater seas
• Analysis of fossils and species distribution helps infer climate changes
• Fossils from the same organism reveal ancient continent positions

Trace Fossils and Animal Behavior

• Trace fossils, reveal information on stride length and shape of the prints of organisms
• Tracking reveals speed
• Groups of tracks may indicate social behavior, size, as well as the adults and young
• Burrow nests reveal behavior
• Crocodiles provide insight into egg burial

Galapagos Finches and Evolution

• Scientists study the relationship between environment and bird populations on a remote island to create a natural laboratory for studying changes
• Galapagos finches were studied, where scientists discovered that beaks size varied
• Beak size depended on diet
• Drought increased ground finches beak size
• Average finches beaks increase by 4%
• The birds are examples of natural selection

Species Diversity and Extinction

• The estimates of species on Earth range between 8 and 15 million
• Species have become extinct throughout Earth's history
• Fossil evidence points to modern species derived from extinct forms

Darwin and Natural Selection

• Charles Darwin's voyage on the HMS Beagle led him to collect fossils and specimens, which led to questions about species origins and distribution
• Darwin's "On the Origin of Species" introduced the hypothesis of evolution by natural selection
• The book explains where different species came from
• The hypothesis is supported by observed living creatures

Key Observations and Darwin's Conclusions

• All species can produce more offspring than needed
• Environmental conditions affects survival
• Individuals vary
• Darwin's conclusion notes that adapted organisms increase in numbers

Populations and Alleles

• Populations of species interbreed
• Variation is the raw material for natural selection
• Successful traits provide a survival advantage
• Genes determine traits
• Alleles effect how common a characteristic is

Genetic Variation and Adaptation

• A population with high genetic variation is more stable
• Adaptable individual are more likely to reproduce
• Lack of variation causes a population to decline and become extinct

Natural Selection

• Natural selection constantly tweaks traits
• New alleles can introduce new changes or be derived from another population
• DNA encodes information
• Genes determine characteristics
• Reproduction and chromosome contribute to hereditary information

Genes and Proteins

• Alleles control protein production
• Proteins are made of amino acids
• Different genes are caused by mutations
• A mutation is a change in the DNA of a gene

DNA Mutations

• DNA mutations can insert/delete/substitute nitrogen bases
• 3 nitrogen bases are read to indicate amino acids (called a codon)
• Populations interbreed and unique alleles come from new mutations
• Immigrations into a population brings new alleles and genes
• Natural selection determines the persist/disappearance of alleles

How Traits are Determined

• In mutations are harmful reproduction decreases and the mutated traits disappear
• If mutations are beneficial reproduction increases and the mutated traits persist
• Natural selection increases the commonality if desired traits and decreases the commonality of harmful traits
• Evolution depends on what traits survive and reproduce

Species Development

• Species develop due to environmental isolation or pressure to change
• One isolated population develops mutations
• Environmental conditions diverge them

Flu Virus Mutation (Example of Natural Selection)

• Flu causes outbreaks that are tracked
• Flu affects a quarter million Americans a year
• Flu causes death
• Flu vaccines help prevent the effects
• The mutations that result in a new disease strain is natural selection

Evidences of Evolution

• Evolution is a scientific theory backed up my measurements
• Scientific theories are comprehensive explanations and the theory of evolution explains how life changes over time
• Evolution is backed up by huge amounts of evidence, and they are continually refined
• Scientific theories can make predictions about the behavior of phenomena or even the existence of ones that have not been discovered
• Evolutionary theory can predict that the location and existence of fossils and living organisms before they have been discovered

Evolutionary Evidence

• The fossil record supports evolution
• Evolutionary occurs through natural selection
• Fossils record support the view that life has changed over long periods of time
• Most evidence comes from the fossil record, evolutionary trees, embryonic development, and DNA.
• Fossil records are incomplete due to location and the ability to create a fossil
• There are species in the past that remain unknown

Fossils

• Fossils help locate transitional fossils
• The horse tree came from fossil discoveries of extinct species
• In the last few decades, scientists have uncovered part of the mystery as to how whales, which are mammals, evolved as sea creatures

Body Structure and Development

• Homologous structures support evolution and appear in extinct organisms
• Embryos support evolution and appear during development
• Vertebrates are similar during development
• Organism developmental steps do see change over evolution

DNA and Evolution

• DNA traces ancestry and has proven genetic evolution
• By studying DNA, scientists discovered that flamingos are closely related to pigeons
• Similar functions are shared across different genotypes
• All animals form a hollow sphere of cells called a blastula
• Genes quickly generates different evolutionary properties
• Most evidence is inferred from evolution but it has been studied in real time

Pesticide Resistance

• Pesticides initially work
• Resistances develop
• Such resistance exists in DDT
• Resistance develops because resistant species breed and evolve
• Resistance develops in glyphosate

Virus & Bacteria Mutation

• Viruses and bacteria infect
• These replicated attacks come with mutations
• Mutated genes result in increased strength
• HIV resists drugs through quick evolution
• Antibiotics once killed bacteria
• New mutations causes resistance to antibiotic offspring

Australian Cane Toads

• Australian cane toads were introduced to control beetles
• The toads carried deadly predators
• The frogs spread faster and developed stronger legs

Pollution

• Pollution has caused evolutionary conditions due to change
• Evolution has occurred due to conditions
• The peppered moth in Britain is an example of evolution due to pollution
• Coal pollution blackened trees
• Certain mutations of the group had colored wings that aided birds