Evolution Part 2 CHAPTER 11 AND 12

Genetic Variation  A population with a lot of genetic variation has a wide range of phenotypes  This allows the population to have a better chance of survival and adaptation  All the different phenotypes are stored in the populations Gene Pool  Gene pool increases with mutations and recombination  How often an allele shows up in the gene pool is called the allele frequency

Gene Flow  Gene flow : The movement of alleles from one population to another  occurs when individuals move among populations  Can cause and increase in genetic variation  Lack of gene flow can cause two populations to evolve into their own species

Genetic drift  Changes in allele frequencies due to chance  One allele will decrease in frequency and disappear while another allele increases in frequency and becomes fixed or the norm  Bottleneck effect : genetic drift that occurs after and event decreases the size of the population drastically.

Genetic drift  Founder effect: genetic drift that happens after a small number of individuals colonize a new area.

Speciation  The rise of 2 or more species from one existing species  Can happen due to isolation of multiple types  Reproductive: member can no longer mate successfully  Behavioral: difference in courtship or mating behaviors  Geographic: physical barriers to reproduction  Temporal: timing prevent reproduction

Patterns of evolution  Convergent evolution: toward similar characteristics of unrelated species  Divergent evolution : closely related species evolve in different directions

Patterns of evolution  Coevolution: two or more species evolve in response to changes in each other

Patterns of evolution  Punctuated equilibrium: fossil record shows periods of evolutionary bursts followed by long periods of stability  Adaptive radiation: the quick evolution from one ancestor into many diverse species

Geologic time scale  Era : tens to hundreds of millions of years and has a least 2 periods  Period : tens of millions of years. Associated with a rock system  Epochs : smallest units of geologic time and last several million years.

 The time scale is made up of four main divisions called…  _________________ time  _________________ era  These eras are further subdivided into ____________ according to the _________ of organisms living during that time Precambrian Paleozoic Mesozoic Cenozoic periods type

Precambrian Time  First and __________________ division  Comprises _____% of earth’s history  Scientists have discovered __________________ fossils of ____________________ from this time longest 87 microscopic prokaryotes

 The first autotrophs were probably ____________________, meaning that they made food while using the energy stored in chemical _________ Chemosynthetic prokaryotes may have been similar to modern day __________________, which can survive in ___________ environments like hot springs and deep sea ________ chemosynthetic bonds archaebacteria harsh vents

 Approximately _______ billion years ago, _____________________ autotrophs evolved  For example, scientists have found fossils of marine cyanobacteria (blue green) in mounds called _____________________ cyanobacteria 2.5 – 3.5 photosynthetic stromatolites Your text’s date is too late

 What gas do photosynthetic organisms release into the atmosphere?  This would allow ______________ cells to exist and the ________________ layer, consisting of _______ to form oxygen aerobic ozoneO3O3

The Evolution of Eukaryotes  About _____ billion years ago, the first eukaryotes appeared.  A eukaryotic cell is much _____________ than a prokaryote is, has a complex system of _____________ membranes, and its DNA is enclosed within a ________________. Section 2 The Evolution of Cellular Life Chapter larger internal nucleus

 Almost all eukaryotic cells have _____________________, while eukaryotic plant cells have _____________________  So how did eukaryotic cells acquire all of these extra organelles?  Scientists hypothesize that ancient ____________ began working together in _______________ relationships, and eventually became ________________ upon one another mitochondria chloroplasts prokaryotes symbiotic dependent

 For example, a large prokaryote may have ingested a smaller _________________ prokaryote that started acting as a ____________________  They also may have ingested photosynthetic bacteria, which started acting as ________________ aerobic mitochondrion chloroplasts

 This idea is called the theory of __________________ and was proposed by Lynn ________________ in the 1960s  “Endo” means ______ and refers to smaller prokaryotes moving into larger ones endosymbiosis Margulis “in”

Endosymbiosis  The following four observations support the theory of endosymbiosis 1. Mitochondria are about the same _______ as most eubacteria, and chloroplasts are the same size as some cyanobacteria. 2. Mitochondria and chloroplasts have _________________ DNA similar to the DNA found in bacteria. Section 2 The Evolution of Cellular Life Chapter 12 size circular

3. Mitochondria and chloroplast both have _______________ that are similar to bacterial ribosomes. 4. Like bacteria, chloroplasts and mitochondria _____________ by simple ___________. This replication takes place __________________ of the cell cycle of the host cell. Section 2 The Evolution of Cellular Life Chapter 12 ribosomes reproducefission independently

Multicellularity  Towards the ________ of Precambrian time, multicellular life evolved  While the unicellular body plan has been very successful, multicellularity has several __________________ Section 2 The Evolution of Cellular Life Chapter 12 end advantages

 Multicellular life was first present in Kingdom __________________  Most protists are unicellular _________________, but some multicellular organisms, like __________________ are classified as protists Protista eukaryotes seaweed

Paleozoic Era  The Paleozoic era began with the ______________ period  This era is marked by an explosion of ___________, or the evolution of many ______________  As a result the Cambrian period is often called the Cambrian _________________ Cambrian diversity species explosion

 Many unusual marine organisms lived in the shallow Cambrian _________  Their fossils have been found in an area of Canada called the _______________ Shale sea Burgess

 The ______________ period followed the Cambrian period…  Many different animals continued to abound in the seas, including __________  At the end of this period, the _____ of five ______ extinctions occurred, meaning that a ___________ number of different species became extinct at the same time  Mass extinctions are observable in rock layers when fossils _________________ from one layer to the next Ordovician fish 1st mass large disappear

The Ozone Layer  Earth’s ________ gradually became a _____________ place to live because the ozone layer protects the earth from the sun’s _____________________ rays  The first multicellular organisms to live on land appeared _____ ______________ years ago Section 3 Life Invaded the Land land safer ultraviolet 430 million

Mesozoic Era  Consists of three periods  _______________  At the beginning of this era, reptiles with complex ____________ and legs positioned __________ their bodies gave rise to _______________ around the same time _______________ evolved Jurassic Triassic Cretaceous teethbeneath mammals dinosaurs

Mammals and Birds  Birds may have evolved from _____________ dinosaurs during or after the Jurassic period.  After the dinosaurs became extinct, birds and mammals became the _________________ vertebrates on land  After mass extinctions, competition temporarily _________________, allowing different organisms to survive and evolve flying dominant decreases

Cenozoic Era  ____________ and shortest era so far Cenozoic Era Tertiary Quarternary The modern human species, __________ ___________ may have appeared as recently as ___________ years ago Present Homo sapiens 200,000