Natural Selection and the Evidence for Evolution The
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Natural Selection and the Evidence for Evolution The theory of evolution is the most fundamental concept in biology.
What is the origin of evolution? • Fossil records have been important to science since the 18 th century. • Fossils have formed concepts & answers questions • Several ideas have been proposed but only 1 ideas accepted today by scientists.
Early scientists proposed ideas about evolution. • Evolution is the biological change process by which descendants come to differ from their ancestors. • A species is a group of organisms that can reproduce and have fertile offspring.
Three theories of geologic change set the stage for Darwin’s theory. • 1. Catastrophism: Volcanoes, Floods and Earthquakes once believed responsible for mass extinction and land formation • 2. Gradualism: The idea that changes on earth occurred in small steps over long periods of time • 3. Uniformitarinism: Geological processes over long periods of time cause the greatest change
• Uniformitarianism is the prevailing theory of geologic change.
Charles Darwin and the Theory of Evolution
Charles Darwin (1809 -1882) • English scientists-founder of modern evolutionary theory • 1831 – naturalists • Collect, study & store specimens while on ship HMS Beagle • Developed theory to explain how evolution occurs
HMS Beagle
Darwin on HMS Beagle
Snoopy discovers Darwin's "Voyage of the Beagle" is not about his favorite dog, but about biological evolution
Darwin on the HMS Beagle • He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey. • As the ship’s naturalist, Darwin studied and collected biological and fossil specimens at every port along the route • For the next 20 years, Darwin’s work refined his explanations for how species change over time.
In the Galapagos • On the Galapagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere. • He realized that individuals struggle to compete in changing environmental conditions.
Galapagos tortoise are the largest On Earth, different from other Tortoises in body size and shape Galapagos finch Is adapted to feed On cacti. Galapagos marine iguanas Eat algae from the ocean Large claws help to cling To slippery rocks
Darwin observed differences among island species. • Variation is a difference in a physical trait. – Galápagos tortoises that live in areas with tall plants have long necks and legs. – Galápagos finches that live in areas with hardshelled nuts have strong beaks.
• An adaptation is a feature that allow an organism to better survive in its environment. – Species are able to adapt to their environment. – Adaptations can lead to genetic change in a population.
Darwin observed fossil and geologic evidence supporting an ancient Earth. • Darwin found fossils of extinct animals that resemble modern animals. • Darwin found fossil shells high up in the Andes mountains.
Darwin continues his studies How did this help Darwin? • He knew that many species produced large number of offspring • He also knew that such species had not overrun Earth. • Only some individuals survive the competition and produce offspring Darwin proposed Natural Selection as a mechanism for Evolution
Artificial Selection artificial selection is the process of intentional or unintentional modification of a species through human actions which encourage the breeding of certain traits over others Darwin hypothesis that there was a force in nature that worked like artificial selection
Several key insights led to Darwin’s idea for natural selection. • Darwin noticed a lot of variation in domesticated plants and animals. • In artificial selection humans can select specific traits through breeding neck feathers crop tail feathers
Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. • Heritability is the ability of a trait to be passed down. • There is a struggle for survival due to overpopulation and limited resources. • Darwin proposed that adaptations arose over many generations.
Natural selection explains how evolution can occur. • There are four main principles to theory of natural selection. – variation – overproduction – adaptation – descent with modification • About 11, 000 years ago, large cats faced extinction due to food shortage in mammals so they had to eat reptiles. • In the Jaguar population, teeth and jaw size became an important variation for survival
• Some natural variations are 1. Variation heritable • Some Jaguars may be • Over time, offspring with certain variations make up born with a slightly most of the population and larger jaws and teach may look entirely different which is directly due from their ancestors. to variation in the population • VARIATION
2. Overproduction • Many offspring will increase the chance of competition between organisms • OVERPRODUCTION • A Jaguars may produce many offspring but few will survive due to competition for resources
3. Adaptation • When an organism needs to compete against its environment for survival • ADAPTATION • According to Darwin’s theory, adaptations in species develop over many generations.
4. Decent with Modification • Overtime Natural selection • Large teeth and jaws become will result in species with a heritable trait adaptations that are well suited for survival and reproduction in an environment • More individuals will have the trait over time as long as the environmental conditions do not change • Fitness is the measure of survival ability and ability to produce more offspring.
Other structural adaptations • Mimicry is a structural adaptation that enables one species to resemble another species
opossum plays possum well Butterfly markings mimics predators eyes Caterpillar mimics Bird droppings
1. Batesian Mimicry • When a harmless animal resembles a harmful animal. • Example: the king snake resembles the coral snake
2. Mullerian Mimicry • When two or more dangerous or distasteful species look similar • Yellow Jacket • Wasp
Caterpillar mimics a viper In both looks & movement The tasty Viceroy Butterfly (left), Mimics the bitter tasting Monarch on The Right
Camouflage • Camouflage allows animals to blend with their surroundings Tartan Hawk fish – blends with Bright gorgonian fans A narrow-headed frog native to Madagascar, blends with the mud & Tree trunks in its environment
Its’ difficult to see in its environment • Disruptive coloration of zebras
Can you spot the Snow Leopard?
Evidence for Evolution
Evidence for evolution in Darwin’s time came from several sources. • 1. Fossils provide evidence of evolution. • Fossils in older layers are more primitive than those in the upper layers.
• Extinct fossils resemble modern animals • This shows common ancestry Fossils are important in Evolution Because they provide a record of early life and history
• 2. The study of geography provides evidence of evolution. – island species most closely resemble nearest mainland species – populations can show variation from one island to another
• 3. Embryology provides evidence of evolution. – identical larvae, different adult body forms – similar embryos, diverse organisms • Larva • Adult crab • Adult barnacle
• 4. The study of anatomy provides evidence of evolution. – A. Homologous structures are similar in structure but different in function and are evidence of a common ancestor.
– B. Analogous structures have a similar body parts in function, but no evidence of a common ancestor • Fly wing • Bat wing
• C. Vestigial structures are body structures in a present day organism that no longer serves its original purpose, but was useful to the ancestor. • Ostrich wings • Human appendix, wisdom teeth, tailbone
Natural Selection in Populations, not individuals, evolve.
Natural selection acts on distributions of traits. • A normal distribution graphs as a bell-shaped curve. – highest frequency near mean value – frequencies decrease toward each extreme value • Traits not undergoing natural selection have a normal distribution.
Natural selection can change the distribution of a trait in one of three ways. • 1. Directional Selection • 2. Stabilizing Selection • 3. Disruptive Selection
– Directional selection favors phenotypes at one extreme. Normal variation Selection for longer beaks
– Stabilizing selection favors the intermediate phenotype (average individual). Selection for average size spiders Normal variation
– Disruptive selection favors both extreme phenotypes.
The Effects Of Natural Selection • Natural selection can significantly alter the genetic equilibrium of a population’s gene pool over time • Significant changes in the gene pool could lead to the evolution of a new species over time
The isolation of populations can lead to speciation. • Populations become isolated when there is no gene flow. – Isolated populations adapt to their own environments. – Genetic differences can add up over generations.
• Reproductive isolation can occur between isolated populations. – members of different populations cannot mate successfully – final step to becoming separate species • Speciation is the rise of two or more species from one existing species.
Speciation • The evolution of new species, a process called speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment.
• Geographic barriers can cause isolation. – called geographic isolation – physical barriers divide population • Temporal barriers can cause isolation. – called temporal isolation – timing of reproductive periods prevents mating
Geographic Isolation • Geographic isolation • https: //www. youtube. com/ occurs whenever a watch? v=kc. Sd 4 MUQU 2 o physical barrier divides a population Isolated habitat fragments are similar to islands in the way in which the species living there are effected.
Evolution through natural selection is not random. • Natural selection can have direction. • The effects of natural selection add up over time.
• Convergent evolution when two distinct species with differing ancestries evolve to display similar features • Has analogous structures, and are NOT closely related
• Divergent evolution when closely related species evolve in different directions they become increasingly different. • kit fox • red fox • ancestor • Ex: Red Fox and Kit Fox though closely related they have developed different characteristics based on the environment they live in
Diversity in a New Environment Divergent evolution occurs when populations change as they adapt to different environmental conditions, eventually resulting in new species.
Species can shape each other over time. • Two or more species can evolve together through coevolution. – evolutionary paths become connected – species evolve in response to changes in each other Coevolution can occur in beneficial relationships.
• Coevolution can occur in competitive relationships, sometimes called evolutionary.
Species can become extinct. • Extinction is the elimination of a species from Earth.
• Background extinctions occur continuously at a very low rate. – – occur at roughly the same rate as speciation usually affects a few species in a small area caused by local changes in environment A steady rate of natural extinction • Species that are unfit to survive die out
• Mass extinctions are rare but much more intense. – destroy many species at global level – thought to be caused by catastrophic events – at least five mass extinctions in last 600 million years • Can be a single event or a concentrated period of time
- Natural selection definition
- Types of natural selection in evolution
- Evolutionary mechanisms
- Natural selection vs evolution
- Similarities
- Natural selection vs artificial selection
- Artificial selection vs natural selection
- Disruptive selection.
- Natural selection vs artificial selection
- Anatomy and embryology evidence of evolution
- Evidence of evolution of remnants and impressions *
- How can class evidence be useful
- Two way selection and multiway selection in c
- Multiway selection in c
- Mass selection
- Speciation
- Evidence of evolution
- Evidence for evolution doodle notes
- Section 15-2 review evidence of evolution answer key
- Common descent
- Convergent evolution definition
- Embryology evidence
- What are the 4 types of evidence for evolution
- What are the 4 types of evidence for evolution
- Types of evolution
- What does amber
- Evidence of evolution stations answer key
- Lamarck's theory
- Embryology evidence of evolution
- Evidence for evolution
- Charles darwin
- 6 evidences of evolution
- Evidence of evolution
- Fish tail bird
- Indirect evidence of evolution
- Molecular biology evidence of evolution
- 5 evidence of evolution
- Evolution berkeley
- Evolution types
- Natural selection and drug resistance
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- Secondary sources
- Primary evidence vs secondary evidence
- Secondary sources
- Primary evidence vs secondary evidence
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- Class vs individual evidence
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- Ecological fallacy
- Balancing selection vs stabilizing selection
- K selection r selection
- What is exponential growth in ecology
- Natural capital and natural income
- Requirements for natural selection
- 4 principles of natural selection
- Stabilizing selection definition
- Genetic drift
- Different types of natural selection
- Natural selection theory
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- Bird beak natural selection lab answers
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- Microevolution