Natural Selection

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” Charles Darwin Inference: Those organisms that are better adapted to their environment have a greater likelihood of surviving to adulthood and passing these characteristics on to their offspring. Survival of the “fittest.” Survive and Reproduce

There are three requirements for natural selection to occur Overproduction=organisms produce more offspring than needed and not all offspring will survive Offspring will compete for resources 2. Variation: Each individual has an unique combination of inherited traits. Adaptation: an inherited trait that increases an organism’s chances of survival 3. Competition: Individuals COMPETE for limited resources: Food, water, space, mates Natural selection occurs through “Survival of the fittest” Fitness: the ability to survive and reproduce Not all individuals survive to adulthood

Ex: Bottleneck Effect and Founder Effect Genetic drift: Is the change in the gene pool of a population due to a random occurrence. (Reduces genetic diversity) Ex: Bottleneck Effect and Founder Effect A) Bottleneck = any kind of event that reduces the population significantly..... earthquake....flood.....disease.....etc.… B) The Founder Effect: A founder effect occurs when a new colony is started by a few members of original population. Small population that branches off from a larger one may or may not be genetically representative of the larger population from which it was derived. Only a fraction of the total genetic diversity of the original gene pool is represented in these few individuals.

Let’s Work together: Natural Selection A scientist studied the population of a certain species of birds based on their tail length. Initially, most of the birds had medium-length tails, but tail lengths ranged within the species from short to long. Two years later, the study was performed again on the same species of birds. An illustration of the birds with different tail lengths and graphs of the data are shown below. Based on the above data, what inference can most likely be made about this species of birds over the 2 year period between studies? A. A new predator arrived that preferred birds with medium-length tails. B. Birds with long-length tails did not have the genetic variation to survive. C. A disease afflicted the birds causing the birds with short-length tails to die out. D. An evolutionary change occurred where birds with short-length and medium-length tails grew long-length tails. Answer A

Check your answers 1-B 2-A 3-D 4-C 5-C 6-B

CELL STRUCTURES

All living things are made of cells All Cells Come from pre-existing cells Cells are the basic units of structure and function of living things

How are cells classified? What are the two major types of cells? What structure is present in one type, but absent in the other? What are some examples of eukaryotic cells? How could you determine whether an unidentified cell was prokaryotic or eukaryotic?

Plant Cell Structures common to most eukaryotic cells. These organelles found in animals, plants, protists, and fungi. Structures found plants only. Cell wall. Chloroplasts, Large Central Vacuole

Isotonic Hypertonic Hypotonic

Cell Membrane/Plasma Membrane Semi Permeable – some things can go through others cannot Phospholipid bilayer

What is Classification? Classification is all about organizing information so that we can easily learn about organisms and correctly identify new organisms that we discover

How do we classify organisms? We classify organisms based on evolution and genetics.

For example… In the past, bacteria and Archaea were in the same group (called Monera) Later scientists realized that their evolutionary history and DNA are very different Now they are in two different groups

For example… Fungi and plants were originally classified in the same group They looked similar and both are non-motile HOWEVER, their evolution and DNA are very different, and one is an autotroph while one is a heterotroph

What other important characteristics do we use to classify things? Cell type Cell structure Number of cells Mode of nutrition

Cell Type Prokaryotic vs. Eukaryotic

Cell Structure Do the organism’s cells have a cell wall or nah? What is the cell wall made of?

Number of Cells Unicellular (the organism’s body only has one cell) OR Multi-cellular (the organism’s body has two or more cells)

Mode of Nutrition Autotrophic (makes its own food) OR Heterotrophic (eats other organisms)

NO NO NO UNI YES YES YES YES NO YES NO UNI Cell wall SOME SOME DOMAIN Archaea Bacteria Eukarya KINGDOM Archaebacteria Eubacteria Protist Fungi Plant Animal CELL TYPE Do they have a nucleus? NUTRITION Do they make their own food? # OF CELLS Are their bodies 1 cell or many? CELL STRUCTURE Are there other special characteristics? NO NO YES YES YES YES NO NO YES NO SOME SOME MOST ARE UNI MULTICELLULAR UNI UNI Cell wall (peptidoglycan) Cell wall (chitin) No Cell wall Cell wall Cell wall (cellulose) Some cell walls, some not

Let’s Practice Together Which characteristic could be observed in an organism classified in Kingdom Protista? cells that lack distinct, membrane bound, organelles B. unicellular and multicellular organisms, some plant like, some animal like. C. flowers used as a method of reproduction D. 100% multicellular bodies organized into organ systems

Check Your Answers! C D B A