Observation Inference Observation An observation is gathering information

Observation & Inference

Observation • An observation is gathering information about events or processes. • They can be quantative which are measurable or countable or they can be qualitative which are describable and not numerical. • Observation is the skill of describing events.

Inference • An inference is a conclusion or deduction based on observations. • Making an inference is the process of drawing a conclusion from given evidence. Practice: • Observations: • A student is in a wheelchair • The student has a cast on their leg • The student is wearing a football shirt • Inference = ? – The student broke his leg while playing football.

FRAME 1 Look at these two sets of animal tracks. What are 3 OBSERVATIONS Make an INFERENCE

Now what do you think? FRAME 2 Make 3 OBSERVATIONS Make an INFERENCE

Now what do you think? FRAME 3 Make 3 OBSERVATIONS Make an INFERENCE

Truth: Evolution is just a theory. • In everyday language, theory is often used to mean a hunch with little evidential support. Scientific theories, on the other hand, are broad explanations for a wide range of phenomena. • In order to be accepted by the scientific community, a theory must be strongly supported by many different lines of evidence. • Evolution is a well-supported and broadly accepted scientific theory; it is not ‘just' a hunch.

Misconception: Evolution is not science because it is not testable.

Truth: Science is not always testable. • Many scientific investigations do not involve experiments or direct observation. – Astronomers cannot hold stars in their hands and geologists cannot go back in time, but both scientists can learn a great deal about the universe through observation and comparison. – In the same way, evolutionary biologists can test their ideas about the history of life on Earth by making observations in the real world. • In organisms with short generation times like bacteria or fruit flies, scientists can actually observe evolution in action over the course of an experiment.

Remember: Hypothesis vs. Theory • Hypothesis: Possible explanation for a set of observations or possible answer to a scientific question. • Theory: well tested explanation that unifies a broad range of observations

How is Evolution Supported? 1. The Fossil Record 2. Geographic Distribution of Living Things (Biogeography) 3. Anatomical Evidence a) Homologous Body Structures b) Vestigial Limbs c) Similarities in Early Development 4. Molecular DNA

FOSSILS Evidence for Evolution through studying fossils BRAINPOP on Fossils: http: //www. brainpop. com/science/diversityoflife/fossils/preview. weml

The Fossil Record is Incomplete Fossils = Traces of dead organisms such as footprints, insects, bones, leaf impressions, etc. • The fossil record shows a sequential appearance and disappearance of species • New species have generally appeared gradually, with species becoming more complex over time • Fossils found in rock layers tells us two things: • What the creatures and plants looked like. • How long ago they existed. (Generally the deeper, the older. ) • The fossil record is incomplete. This is because very few species turn into fossils. Most decay away.

Forming Fossils • Not all parts of an animal become fossilized. – It may not be possible to know some details of what an ancient animal or plant was like because many parts of the anatomy may not fossilize. • What color were the scales on this Allosaurus? • Why do scientists not know the answer to this question?

Dating Fossils • • • Radioactive decay determines age. Half-life = how long it takes for half of the radioactive atoms in a sample to decay. Carbon 14 has a half life of 5730 years It would take 5730 years for 12 grams of Carbon 14 to breakdown into 6 grams of Carbon 14. The process of evolution is very slow, and takes thousands of years.

Relative vs. Absolute Dating • The absolute age of a fossil can be determined though radiometric dating and determining the age of the layer of rock in which the fossil was found. • The relative age of a fossil is determined by comparing it to other fossils. • Older layers are found deeper within the earth than newer layers.

Fossil Transitional forms – More evidence • Transitional fossils are bones that contain traits ancestral groups and descendent groups. These link new species to old species • These intermediate fossils give the history of a slow transformation • Example: Whales came from 4 legged animals • It took them 60 million years to evolve into what they are today. There a series of fossils found that show the tail and fins developing slowly and the legs disappearing. Whale Video

Evolution of birds Today’s organisms descended from ancestral species Fossil of Archaeopteryx • lived about 150 mya • links reptiles & birds

Fossil Evidence of Evolutionary change in body size and toe reduction of horses 19

Evidence that Supports Evolution: Biogeography • • • Biogeography: the study of the geographic distribution of species over time – Some plants and animals have similar appearance but are only distantly related Convergent evolution: the independent development of similar structures in organisms that are not directly related Convergent evolution is usually seen in animals and plants that live in similar environments but in different locations. Green Tree Python from Australia Emerald Tree Boa from South America 20

Evidence that Supports Evolution: Biogeography 1. Similar animals on each continent live in similar ecological conditions a. They were exposed to similar pressures of natural selection. b. Because of similar selection pressures, different animals ended up evolving similar characteristics Beaver NORTH AMERICA Muskrat Beaver and Muskrat Coypu Capybara SOUTH AMERICA Coypu and Capybara Coypu

Evidence that Supports Evolution: Biogeography • Divergent Evolution: The process by which an ancestral species gives rise to a number of new species that are adapted to different environmental conditions and are less alike. • Often occurs when a species colonizes a new environment. • Also known as adaptive radiation. • Examples: – Darwin’s Finches. – Brown bears and polar bears

Evidence that Supports Evolution: Anatomical • Descent with Modification- Each living organism has descended, with changes from other species over time • Common Descent- all living things were derived (originated) from a common ancestor.

Evidence that Supports Evolution: Anatomical • Homologous Structures = Structures from different organisms that have different mature forms, but come from the same embryonic origin • homo- = same • -logous = information – same structure on the inside – same development in embryo – different functions on the outside – evidence of common ancestor Ex) Forelimbs of human, cats, whales, & bats

Evidence that Supports Evolution: Anatomical • Analogous Structures – Structures that look similar on the outside and have the same function but have different structure & development on the inside – different origin – no evolutionary relationship Ex) Wing of a bat and wing of a butterfly

Evidence that Supports Evolution: Anatomical Vestigial Structures = structures that are present in an organism but do not serve any function They are remnants of evolutionary past Example: Whales have a pelvis and femur, but they no longer walk on land.

Evidence that Supports Evolution: Anatomical • Pythons have tiny femurs (leg bone) that are vestigial organs

Evidence that Supports Evolution: Embryology 1. Embryology – the study of developing embryos 1. The embryos of vertebrates are very similar during early development. 2. The same groups of embryonic cells develop in the same order and in similar patterns to produce tissues & organs. 3. Common cells & tissues growing in similar ways produce homologous structures. 4. Implies that common genes are involved. Embryos of vertebrates develop gill slits and tails.

Chicken – 2 ½ days Human – 31 days We grow into our “spine”. At first it appears to be tail-like. Pig – 21 days

Human – 9 weeks Pig – 30 days Lemur – 3 ½ weeks The heart dominates the body cavity.

Limb Buds Pig foot – 30 days Human hand – 6 weeks Chicken foot – 5 days

Human – 6 weeks Pig – 30 days Macaque – 4 weeks

Evidence that Supports Evolution: Molecular DNA • AKA Biochemical Evidence • Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences. • This also gives evidence of a common ancestor.

Evidence that Supports Evolution: Molecular DNA • Which primate is most related to Humans?