Evolution Natural Selection and Adaptations Charles Darwin Brain

Evolution, Natural Selection, and Adaptations Charles Darwin Brain. POP

Voyage of Darwin • In the early 1800’s most scientists thought that species were unchanging. • In 1831, Charles Darwin was traveling around Galapagos Islands, he collected specimens and made observations that led him to believe that species changed over time.

So what did Darwin Say? ► Individuals in a population vary in their traits (characteristics); parents pass traits to their offspring. ► Species generally are best suited for their environments. ► Individuals compete over resources when resources become limited. ► Individuals with slightly better adaptations would get more food and are more likely to reproduce and raise their young to maturity.

Darwin’s Finches • On the Galapagos Islands near Ecuador he noticed something about the finches (birds). They were all similar, but had different beaks because they ate different foods.

Any predictions why this was? ► The finches all came from a common ancestor. ► As they migrated to different areas, their food source changed. ► The birds with the most adapted beak for that food source reproduced more often, making that bird type more common. ► This is evolution.

Evolution • Evolution = a change in species over time

How does evolutionary change happen? • 1859 Darwin finally published “On the Origin of Species” • In the book he proposed evolution happened through Natural Selection. • Natural Selection = Organisms best suited to their environment will survive and reproduce Natural Selection Brain. POP

How Natural Selection Causes Evolution • Species = a group of organisms that can interbreed and have fertile offspring • Population = a group of one species living in the same place at the same time Natural selection is a process that happens to populations, not individuals. • • Natural selection occurs when the environment “selects or influences” which species within a population will survive and reproduce based on favorable traits.

Population vs. Individual • Changes in genes (variations) happen to individuals within the population. We can see the variations of traits among different individuals. • Changes in gene frequencies (how often we see the change) happen to populations. Therefore, evolution happens to populations

How can we measure evolution? • A gene pool is all the genes that exist in a population • This means all of the possible alleles in a given species at a given place and time. • The allele frequency is how often the allele or the gene it codes for shows up in a population

Mechanism for Natural Selection • Living things are constantly struggling to survive. • Those with variations (traits) best suited to the conditions of their life and environment are most likely to survive and reproduce. ("survival of the fittest"). • Genetic variations that cause a species to be successful will be passed on to their offspring.

Natural Selection vs. Artificial Selection • Artificial Selection- man selects a trait. Ex) Selective breeding- people select favorable traits in plants and animals to pass to future generations • Natural Selection- nature selects the trait Ex) Survival of the Fittest- The ability to survive and reproduce in your environment.

Fitness The result of natural selection will always improve the fitness between species and its environment using adaptations. • Fitness is a measure of reproductive success. • Those individuals who have the largest number of MATURE offspring are the most fit. •

Adaptations • In natural selection, if nature doesn't “select” or work for the traits you inherited, your species has to options: Die Out or Adapt. • Adaptations are inherited structures or behaviors that help organisms survive and reproduce. • Adaptations are caused by mutations. Adaptations Video

Evolution-related Scientists: ► ► ► James Hutton - Geographical forces shaped the earth and it is millions of years old. Thomas Malthus - His essay proposed that earth’s population will outgrow its resources. Jean-Baptiste Lamarck - One of the first to propose that organisms change over time. Charles Darwin - Sailed on the H. M. S. Beagle, proposing evidence for Evolution. Charles Lyell - Principles of Geography better explained the age of the earth. Alfred Wallace - Collaborated with Charles Darwin, presented to the Linnaean Society

Examples of Adaptations and Natural Selection

Types of Natural Selection • Stabilizing Selection • Favors maintaining allele frequencies • Selects against extreme phenotypes

Examples of Stabilizing Selection • Humans • Babies born at very high and very low birth weights are less likely to survive. • Plants in a population that are very short may not receive as much sunlight. Plants that are very tall may be more susceptible to wind damage. • The number of plants of medium height will increase while the numbers of short and tall plants will decrease.

Types of Natural Selection • Directional Selection • Favors one phenotype over another • Caused by changes in environment (weather, food availability, drought or flood). A B Phenotype B favored over A

Examples of Directional Selection • Finches • Under conditions of drought, larger birds are more likely to survive than smaller ones. • Birds with larger beaks are more likely to survive than birds with smaller beaks. • Allele frequencies for the population (not individual birds) will change.

Types of Natural Selection • Disruptive Selection • Selects for extreme phenotypes and against “average. ” • This can lead to speciation – the process of new species arising

Example of Disruptive Selection • This grass is pollinated by three different pollinators, one that was attracted to short plants, another that preferred plants of medium height and a third that visited only the tallest plants. • If the pollinator for medium height disappeared from an area, medium height grass would be selected against. • The population would have both short and tall, but not medium height plants. • Allele frequencies for the population (not individual plants) will change.

Webbed feet in Ducks • Originally a mutation caused the ducks to have webbed feet. Because ducks live in water, the mutation was advantageous. • Ducks with the mutation were more likely to survive and pass the mutation to the next generation of ducks.

Syndactyly in Humans • Did you know that other animals have mutations for webbed hands or feet? • In humans it is called syndactyly, and it occurs in approximately 1 in 2, 000 to 2, 500 live births.

Syndactyly in Humans • Syndactyly in humans is a dominant allele. • Dominant alleles are always expressed (AA or Aa). • There is no environmental advantage. Webbed toes or fingers do not make humans better able to survive and reproduce in their environment. • Even though the gene for syndactyly is dominant, it has not ever been found in high frequencies because it is not considered favorable. • People have chosen (or selected) not to marry into families with less desirable traits.

Arctic Animals Have Adapted to Reduce Heat Loss Animals in really cold conditions need to keep warm! • Small surface area to volume: Have a compact rounder shape which keep their surface area to a minimum and reduces heat loss. • Well Insulated: Thick layer of blubber for insulation and stores energy when food is scarce. Thick hairy coats keep body heat in and greasy fur sheds water. • Good In Snowy Conditions: White fur for camouflage. Big feet spread weight and prevents sinking in snow or breaking thin ice. Brain Pop: Camouflage

Adaptations to Deter (discourage) Predators • Some plants and animals have armor- like thorns, spines and hard shells • Others produce poisons – like bees and poison ivy Red near yellow will “Kill-a-Fellow” • Some have warning colors to scare off predators – like wasps. Red near Black is a “Friend-of-Jack”

More examples of adaptations that prove natural selection is the reason behind evolution.

Example 1: Antibiotic Resistant Bacteria • Bacteria can become resistant to antibiotics • If someone gets sick they might be given an antibiotic which kills 99% of the bacteria • The remaining 1% that survive are resistant, so when they reproduce they are passing on the resistant gene • If someone gets sick with the resistant bacteria then the antibiotic will not help them Antibiotic Resistance Brain. POP

Example 2: Peppered Moth • Until the 1850’s dark gray moths were rare. Almost all moths were pale white. • In 1850 dark moths started to become more common, usually in the highly industrialized areas with smoke emissions. WHY? Pale tree trunks were made black by the pollution from the factories and dark moths sitting on these trees were better camouflaged from their predators and lived on to reproduce more black moths.

Example 3: Rats Adapt to Beat Poison The poison warfarin was widely used to control the rat population. However, a certain gene gives rats resistance to it, so rats which carry it are more likely to survive and reproduce. The gene has become more frequent in the rat population, so warfarin is not used as much any more.

Scientists ► 1785 - James Hutton – Proposed that the Earth is millions not thousands of years old. ► 1798 – Thomas Malthus –Predicted that the human population will grow faster than the space and food supplies needed to sustain it. ► 1809 – Jean-Baptiste Lamarck – Through the use or disuse of organs, organisms acquired or lost certain traits in their lifetime. The ideas are flawed but he is the first to propose a mechanism explaining how organisms change over time. ► 1831 – Charles Darwin – “The Father of Evolution” published a book entitled “On the Origin of Species” in which he described evolution, natural selection, and fitness. ► 1833 – Charles Lyell – Lyell explained that scientists should use current processes to explain past events in geology because processes occurring now have shaped Earth’s geological features over long periods of time. ► 1858 – Alfred Wallace – Based on his studies with plants and animals, Wallace said that the most fit of a species survived and that the traits which enabled them to survive were then passed down to future generations eventually creating a new species. Agreed with natural selection and evolution.