Evolution & Organismal Diversity PDF

Unit 2: **EVOLUTION AND ORGANISMAL** **DIVERSITY** **EVOLUTION** "Descent with modification" I I inheritance changing traits from generation to generation I. **EVOLUTION** The cumulative genetic change in a **population** of organisms over time The process by which new species form f...

Unit 2: **EVOLUTION AND ORGANISMAL** **DIVERSITY** **EVOLUTION** "Descent with modification" I I inheritance changing traits from generation to generation I. **EVOLUTION** The cumulative genetic change in a **population** of organisms over time The process by which new species form from existing species through variation and **natural selection** A very slow process which requires thousands of years for the transformation of one species into another **GEOLOGIC TIME SCALE** The interval of time occupied by the history of Earth Represents the time frame within which events of the geologic past are arranged Shows the geologic time intervals based on the geologic rock records, which describe the relationships between the events that happened throughout Earth's history **DIVISIONS OF GEOLOGIC TIME** -EON - longest -ERA -PERIOD - based on the forms of life existing at that time -EPOCH - division of the most recent periods **PRE-CAMBRIAN EON** Covers about 88% of Earth's life history Contains evidence of the earliest forms of organisms that first emerged which were probably similar to present-day bacteria -**HADEAN ERA** - Oldest era; Beginning of the Earth -**ARCHAEAN ERA -** Oldest fossils; Characterized by few fossil or mineral evidence that support it **-PROTEROZOIC ERA -** Early life; fossil remains of bacteria and blue-green algae/ cyanobacteria **PHANEROZOIC EON** Spans within the past 541 million years up to the present Linked with the ***Cambrian explosion***, which is a rapid evolutionary event when complex organisms believed to have first evolved on Earth appeared Paleozoic, Mesozoic, and Cenozoic Eras **PALEOZOIC ERA** ***"paleo"*** (ancient or early); ***"zoic"*** (life) Lasted for 300 million years Emergence of invertebrates **MESOZOIC ERA** ***"meso"*** (middle); ***"zoic"*** (life) Lasted for 180 million years Known for being the **Age of Dinosaurs**, although mammals have already evolved during this era **MESOZOIC ERA** ***"meso"*** (middle); ***"zoic"*** (life) Lasted for 180 million years Known for being the **Age of Dinosaurs**, although mammals have already evolved during this era **II. MECHANISMS OF EVOLUTION\ ** **A. NATURAL SELECTION** **"survival of the fittest"** The idea that individuals whose characteristics give them strategies to better survive and reproduce would leave behind more offspring than less welladapted members **CHARLES DARWIN** Conducted a five-year voyage to the Galapagos Island which allowed him to observe the natural world where he has seen for the first time a number of oddities Focused on explaining evolution within the concept of **population** Published his book *"On the Origin of Species"* in 1809 Formulated the **theory of natural selection** which attempted to explain the causes of evolutionary change among organisms **Darwin\'s Theory of Evolution by Natural Selection -- Major Points:\ ** **Overpopulation\ **-More offspring are produced than the environment can support. -Organisms can die from disease, starvation, or being eaten by predators.\ \ **Struggle for Existence\ **-Organisms must compete for limited resources (food, shelter, mates) in order to survive.\ \ **Variation\ -**There are differences (variations) within a species. -These variations are important because they allow natural selection to act on them.\ \ **Survival of the Fittest\ **-Some variations make an organism better suited to survive and reproduce.Those with beneficial traits are more likely to survive and have offspring\ \ **Variations Can Be Transmitted**·\ -Organisms that survive and reproduce pass on their beneficial traits to their offspring. Over time, these traits become more common in the population. [MODES OF NATURAL SELECTION ] **1. Directional Selection:**\ A type of natural selection where one extreme trait is favored, causing it to become more common in the population. **2. Stabilizing Selection:**\ A form of natural selection that favors individuals with intermediate traits, reducing the occurrence of extreme variations. **3. Disruptive Selection:**\ A type of natural selection that favors both extreme traits, leading to the increased frequency of these traits while eliminating intermediate forms. **B. ARTIFICIAL SELECTION** a.k.a. **selective breeding** A process whereby humans intentionally select and breed individuals with desired traits to produce offspring with those desired traits Demonstrates that humans can act as agents of evolutionary change by actively manipulating the genetic composition of populations **C. GENETIC DRIFT** The change in frequency of an existing gene variant in the population due to random chance Primarily affects small, isolated populations which makes the effect strong, causing traits to become overwhelmingly frequent or to disappear from a population **D. MUTATION** The ultimate source of genetic variation, providing the raw material upon which other evolutionary mechanisms act Becomes a source of new traits which produces variations among populations **E. RECOMBINATION** Occurs during **meiosis**, when homologs pair up and exchange segments of genetic materials through a process called **crossing over** Results in new combinations of traits which increases genetic diversity **III. HOW EVOLUTION WORKS\ ** **A. MICROEVOLUTION** Pertains to the minor differences in the genetic level between populations of the same species providing evidence for diversity within individuals **AGENTS OF MICROEVOLUTION\ ** **1. DNA MUTATION** **"Mistakes"** that occur during replication through insertion, deletion, or substitution of a nitrogenous base Seen as a source of genetic variation, which is essential to natural selection **2.1. SEXUAL REPRODUCTION** Produces genetic variation through recombination, which allows segments of the DNA to be randomly rearranged in the chromosomes, generating new combination of genes **2.2. SEXUAL SELECTION** Plays a role in natural selection and is directly related to courtship and mating behaviors Refers to female's selective preference and male competition which can lead to a condition called **sexual dimorphism**, where males and females exhibit distinct morphological characteristics **2.3. NONRANDOM MATING** **"Who mates with whom"** The preference of organisms to mate with relatives who are similar to them than with unrelated members known as **inbreeding** Impacts the distribution of traits in a given population **3. GENE POOL AND FREQUENCY** The entire collection of genes and its traits Refers to the change in allele frequency over a span of time, which further changes the genetic landscape of the population **4. GENETIC DRIFT** Happens when the gene distribution in small populations evolve randomly by chance Observed during catastrophic events, such as floods or fires that kill a portion of the population, and reduce infant survival or mating randomness **EFFECTS OF GENETIC DRIFT\ ** **a. FOUNDER EFFECT** Observed when few individuals become separated from the rest of the population, such as after a natural disturbance, and are able to establish a territory or colony **b. BOTTLENECK EFFECT** Happens when the size of the population is severely reduced, leaving a few surviving individuals to reproduce and reestablish in the new environment **B. MACROEVOLUTION** Pertains to the big changes that can happen in **allele** frequencies among population Focuses on the major differences that have occurred over long periods, which led to a genetic change that allowed a new kind of species to **PATTERNS OF EVOLUTION WITHIN THE SPECIES LEVEL\ ** **a. GENE FLOW** Refers to the movement of alleles (traits) between populations through the migration of individuals Leads to either an increase or decrease in genetic diversity through **immigration** and **emigration\ ** **b. SPECIATION** Involves the formation of new species Happens when populations or a segment of a population become isolated **GEOGRAPHIC ISOLATION** The physical separation of members of a population as a result of changes in an environment Caused by changes such as formation of new lands or new water barriers **REPRODUCTIVE ISOLATION** The inability of formerly interbreedingorganisms to produce offspring May be caused by the difference in ecological needs and breeding conditions among organisms of the same species within the same geographic range **TEMPORAL ISOLATION** Happens in species that occupy different ecological niches Caused by different breeding seasons **BEHAVIORAL ISOLATION** Caused by preferences and differences in complex courtship rituals in the form of mating calls and ritual dances before the female can get attracted **MECHANICAL ISOLATION** Caused by morphological differences of an organisms reproductive organs, which can lead to incompatibility in terms of size and shape of the genitalia during mating **GAMETIC ISOLATION** Caused by the inability of a sperm cell to fuse with an egg cell due to chemical incompatibility E.g., incompatibility between a giant red urchin (*Stronglycentrotus franciscanus*) and purple urchin (*Strongylcentrotus purpuratus*) **PATTERNS OF EVOLUTION ABOVE THE SPECIES LEVEL\ ** **a. DIVERGENT EVOLUTION** Occurs when closely related species divert to new habitats, often as a result of diverging lifestyles, ultimately producing distinct species E.g., evolution of humans and apes from a common primate ancestor **b. CONVERGENT EVOLUTION** Occurs when groups of distantly related lineages tend to evolve similar structures as adaptations to a similar habitat or way of life E.g., resemblance of placental and marsupial mammals that are not closely related **C. EXTINCTION** The total disappearance of all the members of a certain species from the planet Marks the end of a species' life on Earth Occurs when all the members have been wiped out in the planet due to various factors such as habitat loss, introduction of new predators, or new diseases C. **EXTINCTION** [Background Extinction] The gradual process of species becoming extinct [Local Extinction] Occurs when certain population of organisms that are endemic to a place dies [Mass Extinction] A drastic increase in the rate of extinction as large populations of organisms die in a relatively short period **D. ADAPTIVE RADIATION** Happens when several populations of a single species **diverge** all at the same time into a variety of new species **E. COEVOLUTION** Usually observed in predatoryprey relationships as well as those species with close interspecific interactions such as in mutualism and competition Used to describe the case of two or more nonbreeding species affecting each other's survival and evolution **ANCIENT GREEK BELIEF ON EVOLUTION** Suggested that species have been created separately and remained unchanged from the time of their creation until the present time Grounded in the writings of **Plato\ ** **ARISTOTLE** Recognized that organisms on Earth are related to one another in a hierarchy from simple to complex forms *"Individuals in a species are basically identical and can be arranged hierarchically, and species remain the same"* **GEORGE LOUIS LECLERC, COMTE DE BUFFON** Suggested that closely related species may have arisen from a common ancestor Theorized that the change in organisms may have evolved due to changes in the environment or even by chance. **ERASMUS DARWIN** Believed that evolution could occur in organisms as well as in humans Argued that life may have started evolving long before the start of the history of humankind *"Life evolved from one common* *ancestor, which branched off into all* *species we know today* **JEAN BAPTISTE LAMARCK** Proposed the idea that species, including humans, descended from other species Attributed the change to natural laws **(not to miracles)** and proposed a mechanism of how it can all happen **MECHANISMS OF CHANGE** *-***The physical desire of an animal determines how the body will develop into something. Disuse of a certain body part may weaken the organ and could lead to its disappearance.** **THEORY OF ACQUIRED CHARACTERISTICS** States that if an organism uses a particular structure more, it becomes stronger and more developed States that if an organism uses a particular structure less, it becomes weaker, less-developed, and eventually disappears **DARWINIAN THEORIES** Worked independently, drawing almost identical explanations of how the mechanisms of evolution might have occurred Strong advocates of **natural selection** as the primary mechanism of evolution **V. THE EVIDENCE FOR EVOLUTION\ ** **A. PALEONTOLOGY** ***Fossils*** Mineralized/Hardened traces of dead organisms most commonly found in layers of sedimentary rocks Formed when organisms, footprints, or burrows are buried in sand or sediment **FOSSIL RECORDS** The fossils and the order in which fossils appear Provide evidence of when organisms lived on Earth, how species have evolved, and how some species have gone extinct Show how environmental conditions may have changed over time **METHODS USED TO DETERMINE THE AGE OF FOSSILS** **RELATIVE DATING\ ** Determines whether the fossil is older or younger than other fossils Based on where fossils are found in the stratified rock layers **RADIOACTIVE DATING** a.k.a. ***absolute dating*** or ***carbon-14*** ***dating*** ***-*A method that gives an actual date of the rock or period of an event** A method used to determine the age of rocks by measuring its radioactive decay ***Half-life*** -- corresponds to the length of time required for one half of the radioactive sample to decay E.g., ***Carbon-14*** -- 5,570 years **B. BIOGEOGRAPHY** Associated with the continental drift theory Supports evolution by suggesting that several species are found in continents separated by vast oceans and how these species were separated due to the movement of plates **C. COMPARATIVE ANATOMY** **HOMOLOGOUS BODY STRUCTURES** Same ancestor Same structures Different functions Share a common ancestry, similar structures, but different functions **ANALOGOUS BODY STRUCTURES** Different ancestors Different structures Same functions **VESTIGIAL STRUCTURES** Structures found in living things that have no functions or purpose Often homologous to organs that are useful in other species **D. DEVELOPMENTAL EMBRYOLOGY** ***Embryo*** -- an unborn (unhatched) animal in its earliest phases Suggest that certain structures are present in some organisms during the early stage of embryonic development **E. MOLECULAR BIOLOGY** ***Biochemistry*** -- reveals similarities between organisms of different species Supports evolution by suggesting that closely-related species show more similarities in the ***amino acid sequences of their proteins*** Reflects the nucleotide sequence of the gene coding for a specific protein