The Environment and Change Over Time Chapter 6

Evolution: Is defined as the change over time in populations of related organisms. This theory describes the process by which modern organisms have descended from ancient organisms.

Fossil Evidence of Evolution All the fossils ever discovered on Earth make up the fossil record. Most of the species of these fossils are no longer living on Earth. The fossil record only represents a small fraction of all the organisms that have ever lived on Earth.

Fossil formation: Mineralization: usually shell or bone that is replaced by minerals in water. Carbonization: a carbon outline left from a dead organism, due to compression Molds and Casts: an impression or fossil copy of an organism showing its external features Trace Fossils: evidence of an organism’s activities, such as footprints

Determining a Fossil’s Age Relative-Age Dating shows that the more recent, younger fossils are above the older fossils in the Earth’s rock layers Absolute-Age Dating is determined by radioactive decay of unstable isotopes in igneous rocks – this is the most precise measurement

Extinctions Occur when the last individual organism of a species dies.

Extinctions can be caused by environmental changes….. Sudden changes: could be a volcanic eruption, a meteorite impact, for examples Gradual changes: could be a mountain forming due to the slow movement of the Earth’s tectonic plates, the change temperature of the environment, for examples

The theory of evolution by natural selection Proposed by Charles Darwin in the mid 1800’s

Darwin served as a naturalist with the British navy to the Galapagos Islands.

Darwin observed differences between similar species on the different islands What do you notice about the neck length of these tortoises? How would this impact the food that these animals eat?

Darwin was convinced that the neck lengths and shell shapes changed to match the islands’ food sources. Darwin noticed differences in finches as well.

Variation: a slight difference in an inherited trait of individual members of a species. Caused by sexual reproduction (remember meiosis?) Also caused by random mutations in genes

Natural Selection: the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than those without the same variations. This explains how populations change as their environment changes. Those populations that don’t change will die off and become extinct.

Natural Selection has 4 components: Successful reproduction Helpful variation; traits that make life easier to survive Competition; the offspring that obtain enough food, get a mate will be able to survive Selection: the helpful traits will be passed on to the offspring and be passed on to more members of the population

Adaptation: an inherited trait that increases an organism’s chance of surviving and reproducing in its environment

Types of adaptations Structural: involve a physical characteristic (color, shape, size) Behavioral: involve the acts or behaviors of the organisms Functional: involve internal body systems that impact biochemistry

Species evolve adaptations as they interact with their environments… camouflage mimicry Enables a species to blend in with its environment… Is when one species looks like another species…

Artificial Selection Selective Breeding: Is the breeding of organisms for desired characteristics.

Biological evidence of evolution Comparative Anatomy: the study of similarities and differences among structures of living species.

Homologous structures: Body parts that are similar in structure and position but different in function. Indicates that species are related closely.

Analogous structures: Perform a similar function but differ in structure. Not closely related.

Vestigial structures: Are body parts that have lost their original function through evolution. Only kidding, please use figure 16 on page 211

Embryology: The science of the development of embryos from fertilization to birth. Ok, figure 17 goes here.

Molecular Biology Studies gene structure and function. Darwin did not know about genes when he presented his findings. Mutations provide the source of variation upon which natural selection acts.

Similar gene sequences show how closely are related to each other

A Cladogram shows the evolutionary relationships between organisms