Chapter 13, 14, 15 - Evolution

What is a phylogenic tree?

What biologists traditionally use to depict hypotheses about the evolutionary history of species

What is allopatric speciation?

(Greek allos, other, and patra, fatherland) A mode of speciation where the initial block to gene flow seems to have been a geographic barrier that isolated a population

Evolution is not goal directed

- A trend does not imply that evolution is goal directed - Evolution is the result of interactions between organisms and their current environments - If conditions change, an apparent evolutionary trend may cease or even reverse itself

An organisms evolutionary history is documented in its genome

- Can use DNA analyses to assess relationships between groups of organisms that are so phylogenetically distant that structural similarities are absent - Different genes evolve at different times - The DNA coding for ribosomal RNA changes relatively slowly, so comparaisons of DNA sequences in these genes are useful for investigating relationships between taxa that diverged hundreds of millions of years ago - The DNA in mitochondria evolves relatively rapidly and can be used to investigate more recent evolutionary events

Describe how Darwin's voyage on the Beagle influenced his eventual publication of On the Origin of Species

- Finches - Diverse inhabitants of the Galapagos Islands - Collected thousands of plants and animals, as well as fossils - Noted the unique adaptations of organisms - Read the Principles of Geology - Realised that natural forces gradually changed Earth's surface and that these forces are still operating in modern times - Realised the Earth was old and constantly changing

Phylogenetic trees can change as new evidence becomes available

- Phylogenetic trees are hypotheses about evolutionary history - Molecular systematics and cladistics are remodelling phylogenetic trees and challenging some traditional classifications - As new data and new methods for analysing that data emerge, constructing a comprehensive tree of life will continue to challenge systematists

Explain why "Antibiotics have created resistant bacteria" is incorrect

- The use of antibiotics has increased the frequency of alleles for resistance that were already naturally present in bacterial populations. - Nothing was created, everything was already there.

Explain how the eye has evolved in animals

- Vertebrates and squids eyes evolved from a simple ancestral patch of photoreceptor cells through a series of incremental modifications that benefited the owner at each stage. - First there was the simple patches of light sensitive cells that enable animals from light from dark - Then you have eye cups that indicate light direction. - After that, you get a simple pinhole camera-type eye. - Then, eyes with primitive lens. - Finally, a complex camera-type eye like humans and squids.

Trace patterns of descent through an evolutionary tree diagram, locating the common ancestors of various groups

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Why does natural selection not fashion "perfect" organisms?

1. Selection can act only on existing variations 2. Evolution is limited by historical constraints 3. Adaptions are often compromises 4. Chance, natural selection, and the environment interact - With all these constraints, we cannot expect evolution to craft perfect organisms - Natural selection operates on a "better than" basis

Genetic drift

A change in the gene pool of a population due to chance Two situations Bottleneck effect: A drastic reduction in population size and change in allele frequencies - Exp. Earthquakes, floods, or fires Founder effect: Differences in the gene pool of a small colony compared with the original population - Exp. When a few individuals colonize an isolated island or other new habitat. The smaller the group, the less likely the genetic makeup of the colonists will represent the gene pool of the larger population they left

What is adaptive radiation and describe 3 types of opportunities that might set the stage for adaptive radiation?

Adaptive radiation - The evolution of many diverse species from a common ancestor - Periods of evolutionary change in which may new species form whose adaptations allow them to fill new habitats or community roles - Adaptive radiation followed each mass extinction when survivors became adapted to the many vacant ecological niches Types of opportunities: - A few organisms colonize new, unexploited areas - When environment changes cause numerous extinctions, opening up a variety of opportunities for the survivors - Isolated island chains - No competitors - New habitats and food sources - The evolution of new structures

Compare artificial selection and natural selection

Artificial selection - A process where humans modify other specifies by selecting and breeding individuals that possess desired traits Natural selection - A similar selection of artificial selection, except in nature. - Two observations, two inferences

Use cladistics to design a phylogenic tress

Cladistics - The most widely used method in systematics Clades - A group of species that includes an ancestral species and all its descendants Monophyletic - A clade, such an inclusive group of ancestor and descendants, be it a genus, family, or some higher taxon is said to be this (meaning single tribe). Shared derived characters - New traits Shared ancestral characters - The original traits present in ancestral groups Shared derived characters distinguish clades and thus the branch points in the tree of life Ingroup - The group of taxa that is actually being analyzed Outgroup - A species or group of species that is known to have diverged before the lineage that contains the groups we are studying

Compare and contrast convergent and divergent evolution

Divergent evolution: The process of two or more related species becoming more and more dissimilar - Related species getting more separated from each other Convergent evolution: Species from different evolutionary branches may come to resemble one another if they live in similar environments and natural selection favors similar adaptions. - Not related species getting more similar to each other

Explain how scientists hypothesise early Earth conditions and the events that led to the origins of life

Early Earth Conditions - Young planet Earth probably began as a molten mass. The mass then sorted into layers of varying densities, with the least dense material on the surface, solidifying into a thin crust - The first atmosphere was probably thick with water vapor, along with various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide - Lightning, volcanic activity, and ultraviolet radiation were much more intense Events - Observations and experiments have led scientists to hypothesize that chemical and physical processes on early Earth could have produced very simple cells through a sequence of four main stages: 1. The abiotic (nonliving) synthesis of small organic molecules, such as amino acids and nucleotides 2. The joining of these small molecules into macromolecules, including proteins and nucleic acids 3. The packaging of these molecules into "protobionts," droplets with membranes that maintain an internal chemistry different from that of their surroundings 4. The origin of self-replicating molecules that eventually made inheritance possible -1953, Stanley Miller performed experiments that showed that amino acids and other organic molecules could be formed under conditions believed to simulate those of early life.

Give some examples of natural selection and explain how it is more of an editing process than a creative process

Examples: - Blue-footed boobies - Insects that evolve in different environments (A flower mantid in Malaysia and a leaf mantid in Costa Rica) ** Finches in the Galapagos Islands (Beak sizes, seed sizes, and dry or wet years) ** Pesticide resistance in hundreds of insect species - A pesticide does not create alleles that allow insects to resist it. Rather the presence of the pesticide leads to natural selection for insects already in the population who has those alleles

Explain the evidence for evolution

Geographic distribution of species (biogeography) - Darwin noted that Galapagos animals resembled species of the South American mainland more than they resembled animals on islands that were similar but much more distant - Logical explanation was that the Galapagos species evolved from animals that migrated from South America Comparative anatomy - Anatomical similarities between species give signs of common descent Comparative embryology - Compares and contrasts embryos of different species Molecular biology - Biologists can read a molecular history of evolution in the DNA sequences of organisms Fossil record - The sequence in which fossils appear within layers of sedimentary rocks ^^ Provides some of the strongest evidence of evolution - The rate of sedimentation and the types of particles that settle vary over time. As a result, the rock forms into strata, or layers. - Younger strata are on top of older ones; thus, the relative ages of fossils can be determined by the layer in which they are found - Fossil record reveals the historical sequence in which organisms evolved

Explain homology and give some examples of homologous structures

Homology - Similarity in characteristics that results from common ancestry Homologous structures - Anatomical similarities in different organisms, features that often have different functions but are structurally similar because of common ancestry Exp. Vertebrate forelimbs (Human, cat, whale, bat), All vertebrate embryos have a tail posterior to the anus, as well as structures called pharyngeal (throat) pouches The arms, forelegs, flippers, and wings of the different mammals are variations on the anatomical structure of an ancestral organism, structures that over millions of year have become adapted to different functions

Compare and contrast homology and analogy

Homology: Similarities due to shared ancestry Analogy: Similarity due to convergent evolution

Compare and contrast Darwin's phrase "descent with modification" with Lamarck's ideas about evolution

Lamarck: - Proposed that by using or not using its body parts, an individual may change its traits and then pass those changes on to its offspring. - Known as the inheritance of acquired characteristics - Exp. Giraffes and their long necks Darwin: - His theory states that all organisms -animals, plants, fungi, all organisms - are descended from a remote common ancestor. - He stated that all species evolved from earlier species. - Evolution is a remodelling process in which ancestral structures that originally functioned in one capacity become modified as they take on new functions - Organisms change in time, usually very slowly, or evolve overtime to become a new species. - Organisms with superior traits are more likely to survive, thus the future generations will be more like the organisms with superior traits because the slow moving animals die out and cannot reproduce

Molecular clocks help track evolutionary time

Molecular clock - Estimates the actual time of evolutionary events based on the number of genetic changes. It is based on the assumption that some regions of genomes evolve at constant rates

Describe 4 observations and/or inferences that served as a basis for natural selection

Observation #1: Members of a population often vary in their traits, and most traits are inherited from parent to offspring Observation #2: All species are capable of producing more offspring than the environment can support Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference #2: This unequal production of offspring will cause favorable traits to accumulate in a population over generations

What is "microevolution"?

Population - A group of individuals of the same specifies living in the same place at the same time Gene pool - The total collection of genes in a population at any one time Microevolution - A change in the gene pool, evolution occurring on its smallest scale Exp. Insect population and pesticides

Post-zygotic barriers. Give examples

Post-zygotic barriers - Operate after hybrid zygotes are formed Reduced hybrid viability - Most hybrid offspring do not survive. Reduced hybrid fertility - The hybrid offspring of two different species reach maturity and are vigorous but sterile, and therefore unable to bring about gene flow between the parent species Hybrid breakdown - The first-generation of hybrid offspring are viable and fertile, but when these hybrids mate with one another or with either parent species, the offspring are feeble or sterile

Pre-zygotic barriers. Give examples

Pre-zygotic barrier - Prevents mating or fertilization between species Five main types Temporal isolation - Occurs when species breed at different times Habitat isolation - Two species live in the same general area but not in the same kinds of places Behavioural isolation - There is little or no sexual attraction between females and males of different species Mechanical isolation - Occurs when female and male sex organs are not compatible; For instance, the male copulatory sex organs of many insect species have a unique and complex structure that fits the female parts of only one species Gametic isolation - A male and a female from two different species may copulate, but the gametes do not unite to form a zygote

Define species. Explain why this concept is difficult to define

Species - Latin for "kind" or "appearance." A group of populations whose members have the potential to interbreed in nature and produce fertile offspring Others: - Morphological species concept - Classification that is based mainly on observable and measurable physical traits such as shape, size, and other features of morphology (form). - Ecological species concept - Identifies a species in terms of their ecological niches, focusing on unique adaptations to particular roles in a biological community - Phylogenetic species concept - Defines a species as the smallest group of individuals that share a common ancestor and that forms one branch on the tree of life - It is very difficult to define because there are many situations that do not follow this biological species concept. - Exp. The two different species of cichlids can reproduce together and produce viable offspring - Exp. There is no way to determine whether organisms that are now fossils were once able to interbreed - Exp. This criterion is useless for organisms such as prokaryotes that are asexual in their reproductionor biological it defines a species as a group of population whose members have the potential to interbreed and produce fertile offspring. morphological is like it categorizes the species according to their appearance, ecological is like it focuses on their role in the community, and phylogenetic is like they share a common ancestor

Compare and contrast the three modes of natural selection

Stabilizing selection - Favors intermediate phenotypes - Typically occurs in relatively stable environments, where conditions tend to reduce phenotypic variation Directional selection - Shifts the overall makeup of the population by acting against individuals at one of the phenotypic extremes - Most common during periods of environmental change or when members of a specifies migrate to some new habitat with different environmental conditions - Exp. Insects exposed to pesticides Disruptive selection - Typically occurs when environmental conditions are varied in a way that favors individuals at both extremes of a phenotypic range - Can lead to two or more contrasting phenotypes in a population - Exp. African seed cracker finches

Explain how the phrase "survival of the fittest" differs from the biological definition of fitness

Survival of the fittest - Means direct competitive contests between individuals Biological definition of fitness - The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

What is the current hierarchical classification used? Explain the Linnaeus' binomial naming system

Systematics: A discipline of biology that focuses on classifying organisms and determining their evolutionary relationships Binomial - A two-part name Genus - The first part of a binomial, tells to which a species belongs Species - The second part identifies one within that genus - The first letter of the genus name is capitalized and that the binomial is italicized and latinized In additions to naming species, Linnaeus also grouped species into a hierarchy of categories Family - Group that places similar genera Orders - Puts families into this group Classes - Orders into classes Phyla - Classes into phyla Kingdoms - Phyla into kingdoms Domains - And more recently, kingdoms into domains Danish King Philip Came Over For Good Soup - Ever since Darwin, systematics has had a goal beyond simple organisation: To have classification reflect evolutionary relationships

Gene Flow

Where a population may gain or lose alleles when fertile individuals move into or out of a population or when gametes are transferred between population - Exp. Humans today move more freely about the world than in the past, and gene flow has become an important agent of evolutionary change in previously isolated human populations