Early Life Forms and Evolution

Biology I Study Notes: Overview

• The notes cover various biology topics for Semester 1, including Evolution, Environmental Biology, Cytology, Genetics, Embryology, Taxonomy, and Systematics.

Evolution

• The notes focus on the concept of evolution, tracing its origins from pre-Darwinian times to the modern era.
• Key areas include evolutionary thinking, the origin of Earth and life, and the mechanisms and evidence supporting macroevolution.

Background Information

• Pre-Darwinian thought believed in a young, divinely created Earth with static, unchanging species.
• Post-Darwinian thought proposes an old Earth where species evolve via natural selection and can change, diverge, or go extinct.
• Evolutionary ideas existed before Charles Darwin, with ancient Greeks speculating on animal evolution.
• Empedocles (504-433 BC) hypothesized higher life forms develop from lower ones, and adapted animals replace less adapted ones.
• Aristotle (384-322 BC) suggested a "ladder of nature" arrangement of organisms and spontaneous generation.
• Francesco Redi and Spalanzani disproved spontaneous generation in 1688 by preventing flies from laying eggs on meat.
• Antoni van Leeuwenhoek's microscope in 1683 revealed a microscopic world, rekindling the idea of spontaneous generation.
• Louis Pasteur demonstrated in 1861 that non-sterile techniques explained many "spontaneous generation" examples.

The Pre-Darwinian Period

• Carolus Linnaeus (1700s) believed in the fixity of species, each ideally suited to its habitat and placed on a "Scale of Nature."
• Linnaeus is notable for devising the binomial system of classification (e.g., Homo sapiens).
• Cuvier's catastrophism (late 1700s) explained the fossil record as periodic local extinctions followed by repopulation.
• Lamarck (late 1700s) proposed the inheritance of acquired characteristics, which lacks evidence.

Charles Darwin/Alfred Wallace

• Charles Darwin and Alfred Wallace independently proposed natural selection as the mechanism for evolution, with Darwin publishing "On the Origin of Species" in 1859.
• Erasmus Darwin, Charles' grandfather, had discussed natural selection in the early 19th century.
• Charles Lyell's Uniformitarianism suggested slow geological processes, implying an old Earth, which supported Darwin's need for long timescales for evolution.
• Thomas Malthus's "Essay on the Principle of Population" inspired Darwin to consider differential survival based on resource limits.
• Darwin and Wallace posited animals change over time to adapt and are related through common descent.

Modern Evolutionary Thought

• Creationism, or the Biblical idea of Earth being 6,000 years old, is still a religious principle, but is not a scientific fact due to reliance on belief.
• Intelligent Design merges Scientific Evolution and Religious Creationism, stating that Evolution occurred, but was directly guided by God.
• "Neo-Darwinism" incorporates advances in molecular genetics into theories of evolution.

Origin of Earth and Life

• The universe began about 15 billion years ago with the "Big Bang," and the solar system gradually formed over the last 10 billion years.
• The primitive Earth was fully formed about 4.5 billion years ago.
• The early Earth was molten and cooled into layers, with heavier elements accumulating at the core and lighter elements forming the mantle.
• Volcanic eruptions and cooling formed the thin crust.
• The gravitational forces was able to retain an atmosphere formed from degassing.
• Water vapor condensed into rain, forming oceans, although high temperatures and meteorite bombardment were factors against stability.
• The early atmosphere lacked free oxygen, and the ozone layer was absent, meaning harmful exposure to sun.

Conditions for the Origin of Life

• Absence or near absence of oxygen.
• External energy sources such as solar radiation, lightning, heat from volcanoes and meteorites, and radioactivity.
• The existence of chemical molecules for energy sources to act upon.
• A large period of time for these conditions to synthesize to produce the first life forms.

Stages in the Origin of Life

• Oparin (1938): simple organic compounds could spontaneously be created with strong energy sources.
• Stanley Miller (1953): experiments proved can combine gases to make organic molecules with electricity.
• Polymers evolve when simple compounds exposed to high temperatures combine, making longer chains.
• Amino acids can combine into polypeptides on hot clay surfaces.
• Coacervates formed when proteinoids returned to water.
• Primitive cells developed when coacervates absorbed self-replicating RNA strands.

The Evolution of Complex Cells

• The first cells were prokaryotic heterotrophs absorbed available organic compounds from environment.
• Chemosynthetic and photosynthetic autotrophs evolved and obtained energy from oxidizing inorganic compounds and the sun.
• Cyanobacteria evolved “modern” photosynthesis using water and releasing oxygen into atmosphere.
• The increasing amount of oxygen led to a protective ozone layer and allowed life to live towards surface and led to dominate the Earth.
• Eukaryotes developed, evolving from a membrane which encloses genetic component.
• Organelles developed in Eukaryotes in result of the Endosymbiont hypothesis.

The Geological Time Scale

• Sedimentary rocks expose the earth and the particles cement by lime, silica or iron and rocks again.
• William Smith, Georges Cuvier and Alexandre Brongniart discovered same age rocks with same fossils.
• Time scale was during the 1700s based upon observations of fossils in rock layers.
• Eras and periods are characterized by animals that lived of time and named from remians of fossils.
• Prefixes Palaco- mean 'old', Meso- means 'middle' and Ceno- means 'Recent'.

The Developement Of Complex Life

• Little fossil evidence is available of life that occurred before the Cambrian because ancient fossils were destroyed.
• The Palaeozioc Era began roughly 570 million years with Cambrian, and life moved on in the forms of algae.
• The Carboniferous period evolved Amniotes- first Reptiles.
• During the Permian Period, the therapsids appeared which evolved mammals etc.
• The Mesozioc Era is known as the Reptiles.
• At the end of Triassic period, the origin of small insectivorous mammals.

Our Wandering Continents

• The anorganic earth has gradually changed due to continual movement with continental drift/tectonic plates.
• Core of the molten magma and metal spins continually and cause the Earth's magnetic field.
• There are twelve large plates and 20 smaller floating on mantle and move causing Earthquakes.
• Pangaea(Carboniferous Period) formed with all continents untied as super-continent which began to break up at start of Jurrasic.
• Gondwanaland broke free and drifted northwards.
• Landmasses rising and dropping during ice ages and were previously separate like Panama. .

The Mechanism of Evolution

• Evolution happens when the population changes phenotype(look).
• The change in population in a generation in the genes is called gene pool.
• Evolution changes phenotype of how the genes of members interact.
• Gene pol will only change if influenced by evolution.

Mendelian Inheritance

• Plants and animals receive appearance from both parents.
• Mixing of genes for pink and flowers= offspring with pink flowers.
• Original genetics aren't destroyed during breeding and can recur in later inheritence.
• You have Homologous Chromosomes of each type of chromosome,it also you have two genes that control characteristics phenotype.
• Alleles or "gene states" are different forms of the same gene like eye color.
• Homozygous genes that are same and Heterozygous that aren't the same character.
• Homologous Chromosomes separate with meiosis to another sperm/egg cell.

Hardy-Weinberg Equilibrium

• Allele frequencies that change when the populations change in a generation is the occurance of evolution.
• Microevolution small change in a few generations with Macroevolution leading to animal changes.
• Sexual reproduction alone cannot change allele frequencies in a population, and dominance doesn't change allele frequencies.
• Two generations of a population are in equilibrium if the gene frequencies in them are the same with following formula:
• p² + 2pq + q2 = 1 is a simple probability theory that states (p+q1)
• p² is frequency of homozygous,
• p is frequency of dominant allele
• q² is frequency of homogenous,
• 2pq is the frequency of the heterozygous

Microevolution causes

1. Mutation: create new harmful mutated alleles.
2. Gene Flow: Genes from one population spreading to another.
3. Nonrandom mating occurs: influence mate choice of inbreeding that doesn't alter frequencies byt increases disorders.
4. Genetic Drift (change by single chance alone
5. Natural Selections: better ability to survive and pass on genes better.
6. Inheritenece of fitness of speed, diversity and water conservation lead adaptation, population will adjust

Natural Selections

• Involves some individuals better then others in reproduciong and inherites characteristits.
• Abiotic and biotic environments adapted and interfered can cause the next generation to be better.
• Natural Selection results in a populating adapts.

Natural Selection Occur:

• Directional Selection: shifts direction of population.
• Stabilizing Selection: Aspects of the environment remains the same.
• Disruptive Selection: Extreme and intermidiate phenotype produced.

Section 5: Speciation

• It is a result of accumulate microevolution.
• In otherwords, species is related to share a gene in gene, and they are isolated from other soecies for success
• In order to belong species, indivisuals need to reproduce with others.
• To separate, natural gene flow is prevented in Isolating Mechanisms.
• A zygote is the Diploid product in the cell
• Prezygotic mechanisms prevent mating and fertilizing.
• Postzygotic mechanisms is the offspring that cant survive.

Prezygotic Mechanisms

• Geographical Isolation: separated by means of barriers.
• Habitat'Ecological Isolation: Spiecies live in area and the don't contact each other to mate.
• Temporal/seasons: species occur in same area.
• Mechanical/Genital: Animal and plant genitalia is incompatible.
• Gamele Isolation: sperm cells cannot fertiliza, or recognize cells.

Postzygotic Mechanisms

• Zygote is fused together.
• F2 Fitness: Hybrids live and thrive and may not eat, sleep or reproduce

Types of Speciation

• Allopatric Speciation: occurs from geographical isolations.
• Sympatric Speciation: When people develop withoht going prior geographic isolations.
• Parapatric Speciation: Different selection and slow divertions.

Evidence for Macroevolution

• It may be is useful to recap a fossil and how they be formed:
• Fossils range in thousands to millions of years old.
• Can also be an indirect trace of existence as the fossil recod even seemed to imply that species could change over time.
• Cuvier explained through rapid change.
• Fossils show change with rock depth (soil)

Anatomical Evidence includes Homologous and Analogous structures

• Homologous = basic anatomical develop once in history-forelimb of vertabrae.
• Analogous = serving same function but without commen ancestral structure-wing of bird etc
• Vestigal Structures; reduced anatomical that serve no purpose in one, but serves funciton in relations.
• Eukarytoes: Cells developed a nucleus by invagination of cell membranes
• Analogous structures are structures serving the same function,structures show that in each of the periods

Embryonic Evoltuion

• During embronic development resemble adult conditions.

Explore the origins and evolution of early life forms, including autotrophs and heterotrophs. Understand the role of oxygen in metabolic processes and geological events. Learn about the development of the ozone layer and the formation of supercontinents.