Download Chapter 15 Section 1 Notes

Chapter 15 Section 1 Notes
What is the explanation for the diversity of life?
*a collection of scientific fact, observation, and hypotheses known as evolutionary theory
helped to explain this
*Evolution, change over time, is a process by which modern organisms have descended from
ancient organisms
-theory is a well supported testable explanation of phenomena that have occurred in
the natural world
Charles Darwin contributed the most to evolution
*born in England on Feb. 12, 1809, same day as Abraham Lincoln
*set sail on the H.M.S. Beagle around the world
* on his journey he collected evidence and made observations that led him to propose a
revolutionary hypothesis about the way life changes over time
His Observations
*many plants and animals were suited for their environment
*puzzled by where different species lived and did not live
*found some fossils resembling living things and others did not
*On Galapagos Island he studied tortoises and iguanas (fig. 15-3)
*Darwin observed that characteristics of many animals and plants varied noticeably among
the different islands of Galapagos
Chapter 15 Section 2 Notes
Several scientists’ ideas shaped Darwin’s thinking
*Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the
processes that changed Earth in the past are the same processes that operate in the present
*Hutton proposed layers of rock form slowly with geological processes, saying Earth is more
than 1000 years old
*Lyell’s Principle of Geology: Processes occurring now have shaped Earth’s geological features
*Jean-Baptiste Lamarck proposed is Evolution Hypotheses
1) Tendency Toward Perfection: all organisms move toward complexity and perfection
2) Use and Disuse: organisms could alter the size and shape of particular organs by
using bodies in new ways
3) Inheritance of Acquired Traits: thought acquired characteristics could be inherited
*Problems with Lamarck’s idea
-didn’t know how traits were inherited
-behavior has no effect on heritable characteristics
-and but he did realize organisms adapt to their environment
*Thomas Malthus influenced Darwin
-If human population continued to grow unchecked, sooner or later there would be
insufficient living space and food for everyone
-forces worked against humans including war, famine and disease
-could apply this to plants and animals
Chapter 15 Section 3 Notes
*Darwin began filling notebooks with his ideas about species diversity and the process that
would later be called evolution, however, he did not rush out to publish his thoughts
*In 1885, Darwin received a short essay from Alfred Russell Wallace summarizing the
thoughts on evolutionary change that Darwin had been mulling over for almost 25 years.
-incentive to publish his own work
*1859 Darwin published On the Origin of Species which proposed a mechanism for evolution
has been taking place for millions of years
*mixed feelings were given about the book
Inheritance
*Artificial selection-selection by humans for breeding of useful traits from the natural
variation among different organisms
*In artificial selection, nature provided the variation, and humans selected those variation
that they found useful
Evolution by Natural Selection
*To explain how evolution occur, Darwin developed his hypothesis called Natural Selection
*Struggle for Existence
-members of each species compete regularly to obtain foods, living space and other
necessities of life
-In this struggle, the predators that are faster or have a particular way of catching
prey will catch more than other predators
*Survival of the Fittest
-key factor in the struggle for existence
-fitness: ability of an individual to survive and reproduce in its specific environment
-Darwin proposed that fitness is the result of adaptations
-adaptation is any inherited characteristic that increases an organism’s chance of survival
-Darwin concluded, successful adaptation, enabled organism’s to become better
suited to their environment and thus better able to survive and reproduce
-process known as survival of the fittest
-Concept of fitness was central to the process of evolution by natural selection
-Over time, natural selection results in changes in the inherited characteristics of a
population. Those changes increase a species’ fitness in its environment
*Descent With Modification
-Darwin proposed that over long periods, natural selection produces organisms that
have different structures, establish different niches or occupy different habitats. As a result, species today look different from ancestors. Each species has
descended, with changes, from other species over time
-common descent: all species-living and extinct-were derived from a common ancestor, a
tree of life
Evidence Of Evolution
*Darwin argued that living things have been evolving on Earth for millions of years
*Evidence can be found in:
1) Fossil Records
2) Geographical distribution of living species
3) Homologous structure of living organisms
4) Similarities in early development-Embryology
1) Fossil Records-By comparing fossils from older rock layers with fossils from younger layers,
scientists could document the fact that life on Earth had changed over time (Fig 15-13)
2) Geographical Distribution: species now living on different continents had each
descended from different ancestors. Because some animals on each continent were
living under similar ecological conditions, they were exposed to similar pressures of
natural selection, different animals ended up evolving certain striking features in common
3) Homologous Structure: structures that have different mature forms but develop from
same embryonic tissue (Fig. 15-15)
-Ex. limbs of reptiles, birds and mammals-arms, wings, legs, and flipper vary in form
and function but are all constructed from the same basic bones
-vestigial organs: organ that serves no useful function in an organism Ex. dolphins
look like fish and expect them to use and have gills, but dolphins have lungs like mammals
4) Similarity in Embryology-common cells and tissues, growing in similar ways produce the
homologous structures
Summary of Darwin’s Theory
*Individual organisms differ, and some of this variation is heritable
*Organisms produce more offspring than can survive, and many that do survive do not reproduce
*Because more organisms are produced than can survive, they compete for limited resources
*Each unique organism has different advantages and disadvantages in the struggle for
existence. Individuals best suited to their environment survive and reproduce most
successfully. These organisms pass their heritable traits to their offspring. Others die and
leave fewer offspring. This process of natural selection causes species to change over time.
*Species alive today are descended with modification form ancestral species that lived in
distant part uniting all organisms on Earth into a single tree of life
Strengths and Weaknesses
-offered vital insights to all biological science from disease to ecology
-still debate how new species arise and why species become extinct
-uncertainty about how life began
Chapter 16 Notes
*2 things Darwin didn’t know when he came up with his Theory of Evolution
1. didn’t know how heritable traits pass from one generation to another
2. no idea how the variation appeared
*A gene pool consists of all genes that are present in a population
*Relative frequency is the # of times that the allele occurs in a gene pool, compared with the
# of times other alleles for the same gene occur
Sources of Genetic Variation
1) mutation
2) genetic shifting
*both result from sexual reproduction
*The # of phenotypes (physically look like) produced for a given trait depend on how many
genes control the trait
Single-gene trait: widow’s peak controlled by a gene with 2 alleles
Ex. widows peak is dominant, non widows peak is recessive
Polygenic trait: controlled by two or more genes
*Natural Selection on single-gene trait can lead to changes in allele frequencies and thus
evolution Fig. 16-5, pg. 397
*Natural Selection can affect the distribution of phenotypes
Genetic Drift
*Genetic Drift is random change in allele frequency
*In small populations, individuals that carry a particular allele may leave more descendants
than other individuals, just by chance. Over time, a series of chance occurrence of this
type can cause an allele to become common in a population
Hardy Weinberg Principle
*allele frequency in a population will remain constant unless 1 or more factors cause
frequencies to change
*Genetic Equilibrium: situation where allele frequency remains constant
*5 Conditions are required to maintain genetic equilibrium from generation to generation:
1) random mating
2) population must be large
3) no movement into or out of the population
4) no mutations
5) no natural selection
*If any of these are missing, organisms will change and evolution will occur.
Speciation
Speciation: formation of new species
In order for a species to evolve into a new species the gene pools of two populations must
become separated
Reproductive Isolation: when two populations cannot interbreed and produce fertile
offspring
1) Behavioral Isolation: capable of breeding, but have different courtship or
mating rituals
2) Geographical Isolation: separated by a geographical barrier
3) Temporal Isolation: reproduce at different times
*Speciation in Galapagos occurred by founding of a new population, geographic isolation,
change’s in the gene pool, reproductive isolation and ecological competition
Chapter 17 Notes
The history of life on Earth is filled with mystery, life-and-death struggles, and bizarre
plants and animals as amazing as any mythological creature.
*Technique used to the pieces of the story are “written” in petrified sap of ancient
trees, peat bogs, and tar pits, in polar glaciers called fossils
*Paleontologists: scientists who study fossils
*fossil record: all information about past life
-The fossil record provides evidence about the history of life on Earth. It also shows
how different groups of organisms, including species, have changed over time.
-fossils appear in a certain order
-some fossils appear only in older rocks and some only appear in recent rocks
-99% of all species that have ever live on Earth are EXTINCT: species died out
Fossil Form (fig 17-2)
1) Water carries small rock particles to lakes and seas.
2) Dead organisms are buried by layers of sediment, which form new rocks
3) The preserved remains may later be discovered and studied
Interpret Fossil Evidence
*Many fossils are missing parts, occasionally a whole fossil is found
*Paleontologists need to piece together the missing pieces
*Use relative dating to figure out how old something is
-relative dating: age of fossil is determined by comparing its placement with that of
fossils in other layers of rock (fig 17-3)
-allows paleontologists to estimate a fossil’s age compared with other fossils
-use index fossils to compare the relative ages of fossils
*Radioactive dating is used to date fossils too
-scientists calculate the age of a sample based on the amount of remaining radioactive
isotopes it contains
-half life: length of time required for half of the radioactive atoms in a sample to
decay (fig 17-4)
Geological Time Scale: represents evolutionary time
*After Precambrian Time, the basic divisions of the geologic time scale are eras and periods
-eras: Paleozoic, Mesozoic, Cenozoic
-periods: subdivided eras
Life on Earth and Earth’s History
*Life comes from life
*Current scientific views based on relatively small amount of evidence with the gaps and
uncertainty makes it likely that scientific ideas about the origin of life will change
Biogenesis: all living things come from other living things
Spontaneous Generation: living things are produced from nonliving things
Scientist involved in providing biogenesis: Redi, Spallanzani, Pasteur
Timeline
*Earth began 4.6 Billion Years Ago
*Early atmosphere did not contain oxygen-would have interfered with formation of organic
compounds
*Formation of simple organic compounds: amino acids
*Formation of genetic material
*First cells were probably:
-anaerobic (without oxygen)
-heterotrophic (energy from food gathered)
-prokaryotes (single-celled organism)
-1st cells developed in an environment filled with organic molecules for food
*Autotrophs began to appear when heterotrophs used up their food supply
-used chemosynthesis: make own food using inorganic substances as an energy source sulfur
*Photosynthetic life forms 3 billion years ago
-began to produce oxygen
-oxygen damaged early unicellular organism
-aerobic respiration develops (use of oxygen)
*Ozone layer develops
-first poisonous to plants and animals
-absorbs UV rays
-splitting of oxygen atoms and recombining created 03
*First Eukaryotes (multicellular) form
-sexual reproduction speeds up evolution because genetic variation occurred in gene
shuffling
Precambrian time:
-90% of Earth’s history occurred
-simple anaerobic forms of life
-photosynthetic form added oxygen
-few fossils exist
-life existed in the sea
Paleozoic Era:
-diversity of marine life
-included invertebrates
-vertebrates began to invade land
-mass extinction occurred
*affected both plants and animals
*95 % of complex life disappeared
Mesozoic Era
-increasing dominance of dinosaurs
-flowering plants appeared
Cenozoic Era
-mammals evolved adaptations that allowed them to live in various environments-land, water,
and even air
Macroevolution
Large scale patterns and process that occur over long period of time
Can occur in several ways:
1. extinction: species die out
2. adaptive radiation: over time, small groups of species evolve into diverse organisms
3. convergent evolution: unrelated organisms resemble on common ancestor
4. coevolution: two species evolve in response to change in the other
5. punctuated equilibrium: long stable periods with brief, rapid changes
6. change in development of genes