A Variety of Species - millions of species live on Earth (bacteria to huge sequoia’s) - *Over time, different environments and genetic variation have produced, through natural selection, the variety of organisms that exist today Different Environments - from deep sea to mountain tops - organisms live in each environment - over millions of years, natural selection has produced different species, with adaptations enabling it to live in specific habitat
Habitat - specific environment that provides the things the organism needs to live, grow, and reproduce Genetic Diversity - organisms within same species DO NOT all have identical traits - ex: differences among humans - organisms in a species have different alleles for the genes that govern traits - some genetic differences are result from DNA mutations, others from rearrangement of genes during meiosis - all genetic variations in a species makes up the total “gene pool” of that species
- species with gene pool variety adapt the changes in environment, allowing them to have surviving traits in new conditions - species that are genetically similar have a difficult time surviving in new environments ex: corn crops wiped out by fungus because all corn was same, with no resistance to fungus - genetically similar species are more likely to be destroyed by environmental change
How New Species Form - *A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits - Geographic Isolation - hypothesis that this one of main ways new species formed - isolation happens when members of a species become cut off from rest of the species (ex: river, volcano, mountain) - once isolated, group can no longer mate with rest of species
- Ex of Isolation - Abert’s squirrel (white belly) & Haibab squirrel (black belly) - species are separated by Grand Canyon Inferring Species Relationships - *Scientists have combined the evidence from DNA, protein structure, fossiles, early development, and body structure to determine the evolutionary relationship among species
- Similarities in DNA - scientists compare the genes of different species to determine how closely related the species are - the more similar the DNA (sequence of nitrogenous bases), the more closely related the species are - scientists also compare the order of amino acids in a protein to see how closely related species are - Combining Evidence - recent DNA comparisons show dogs more similar to wolves that coyotes - giant pandas more related to bears, lesser pandas more related to raccoons
Extinction of Species - extinct - no members of that species exist - Extinction & Environment - *Extinction is caused by a change in a species’ environment. The members of the species may not have adaptations' that allow them to survive and reproduce in the changed environment - environments can change by - a disease striking a species - predators over hunting their prey
- Climate change - leading cause of extinction - destroys organisms habitats - Adaptation & Survival - not all organisms & species become extinct due to environmental change - those with the right traits will survive