The Organization of Life Chapter 4 Ms. Cuthrell Ecology 2nd Period

Evolution by Natural Selection 1859, Charles Darwin proposed an answer to the question, “how do organisms become so well suited for their environment?” The answer he proposed is Evolution by Natural Selection

Evolution by Natural Selection Darwin noticed that in a population (same species living in same place) the organisms are slightly different in: Form- how the body is shaped/colored Small beaks vs. Large beaks Function- what the body does Eating small seeds vs. Eating large seeds Behavior- what the organism does Ignoring humans vs. Running away

Evolution by Natural Selection “Survival of the Fittest” In a certain environment, certain traits will help an organism survive These organisms will have more offspring The next generation will have more traits that are like those organisms Over time the population will evolve, so that the traits that help survival will be found in more organisms

Evolution by Natural Selection Darwin’s theory can be summarized in 5 steps: Organisms produce more offspring than can survive The environment is hostile and has limited resources Organisms differ in the traits they have Some traits provide an advantage Each generation will have more organisms with advantageous traits The traits that helps an organism survive are known as adaptations

Evolution by Natural Selection

Evolution by Natural Selection Sometimes different organisms evolve to help each other out This is called coevolution Insects get food by eating the nectar inside flowers The have long straws that help them do this The flowers give off pollen, which attached to the insect When the insect go to another flower it pollinates the new flower

Evolution by Artificial Selection Since the agricultural revolution we have been domesticating animals and crops We breed animals so they have the traits we need them to have Horses = speed/strength cows = quality of meat Dogs = beauty Crops are breed to grow faster, bigger, be disease resistance, different colors, …

Evolution by Artificial Selection This type of selective breeding that is controlled by humans is called Artificial Selection. The Chihuahua is a descendent of the grey wolf.

Evolution of Resistance In our quest to control nature we spray pesticides to kill insects Unfortunately we have used pesticides, so much that insects have become resistant An organism can tolerate a chemical that is designed to kill it

Evolution of Resistance

Genetics Around the same time as Darwin, an Austrian monk, Mendel, was studying pea plants He was trying to understand how different traits are passed from parents to children Mendel breed different types of pea plants together and observed the flower color and type of peas

Genetics Mendel came up with 3 conclusions: There are different forms of the units that control traits (flower color, pea type, eye color, …) For each trait there are 2 units, 1 from each parent If the units are different, then 1 of them is dominant and the other is recessive We have found out since then that the “unit” is a gene

Genetics In order to keep a population healthy, there must be genetic variation Members of a population with different traits (eye color, thick/thin fur, small/large beaks, …) This variation comes in 2 major ways: Mutation Genetic Recombination

Genetics- Mutation A change in the gene of an organism that can be passed to its offspring is a mutation Mutations that effect a single gene can do cause a range of damages These are typically not even noticed If they are noticeable then they are usually severe and cause serious damage Mutations that effect multiple genes usually result in the death of the organism

Genetics- Genetic Recombination Genetic Recombination occurs when organisms reproduce sexually Genes from 2 organisms combine to create an offspring There are approximately 8 million unique genetic combinations in humans If an organism reproduces asexually, then the genetics are exactly the same as the parent Without mutations the population would not evolve

Genetics- Evolution If you look at evolution using genetics, then evolution can be defined as a change in gene frequency in a population Which genes are the most/least common Remember: Individuals do not evolve, populations evolve. The beauty of Natural Selection is in its simplicity It does not require any certain direction or end result It is only guided by random mutations in DNA

Ecosystems Ecosystem All organisms living in an area together with their physical environment All plants, animals, rocks, water, and everything else All living and nonliving things! All ecosystems are connected!

Ecosystems All ecosystems need 5 things to survive: Energy Mineral Nutrients Water Oxygen Living Organisms

Ecosystems Biotic Factors Abiotic Factors Organisms (the living things) and stuff that came from organisms Plants, animals, leaves, bodily waste Abiotic Factors The nonliving part of the ecosystem Air, water, sand, rocks, light, temperature

Ecosystems Organism Species An individual living thing You, me, that bug living on your eyelashes! Species Group of organisms that are closely related and can mate to produce fertile offspring

Ecosystems Population All members of the same species that live in the same place at the same time. Members of 1 population will usually breed with each other rather than with other populations You wouldn’t fly to another country just to find someone to marry

Ecosystems Community A Pond You can belong to more than one community Various species that live in the same place and interact with each other A Pond Plants, fish, insects, animals that live around the pond You can belong to more than one community Birds that migrate during the seasons

Ecosystems

Ecosystems Habitat The place where an organism lives Cactus = desert Waterlily = pond Salamander = damp forest floor