Transcript Lesson 7.1
*Refer to Chapter 3 in your Textbook Learning Goals: 1. I can describe the conditions required for Natural Selection to occur. 2. I can analyze how factors of natural selection and speciation contribute to marine evolution. Marine Evolution: 1st organisms were autotrophs about 3.5 BYA Autrotrophs raised the oxygen in the atmosphere from 1% to 21% With more oxygen, more life was able to diversify on earth Scientist theorize these autotrophs could have began in many places: Tide pools Hot springs Hydrothermal vents Marine Evolution: Natural Selection: the process where organisms with variations best suited to their environment survive. Theory of Evolution: the process where organisms change over long periods of time. Natural Selection: Conditions required for Natural Selection to occur: 1. Struggle for Existence 2. Variation & Adaptation 3. Survival of the Fittest Natural Selection: 1. Struggle for Existence: Cause: If more individuals are produced that can survive… Effect: Than individuals in a population must compete for food, living space, and other necessities Natural Selection: 2. Variation & Adaptation: Variation: when similar organisms show differences in heritable traits Adaptation: an organisms heritable trait that increases it’s ability to survive and reproduce Natural Selection: 3. Survival of the Fittest: Fitness: an organisms ability to reproduce and survive Differences in adaptations can effect an organism’s fitness Survival means that the organism has reproduced and passed the adaptation onto the offspring Example: A group of hippo tangs live together on a coral reef, and one is particularly large because he eats the most algae. Is he the fittest individual? That depends… Consider two scenarios… Example: Scenario 1: They are competing for algae on the reef, and it is who will not starve. Is he the “fittest”? Yes, he is the largest and will be able to fight for algae. Scenario 2: There is a shark feeding frenzy at night and the largest tang cannot fit to hide in the coral. Is he the “fittest”? No, he dies because the sharks can easily find him. Thing to consider: The fittest is based on the conditions a species lives in, and at a given moment! Natural Selection: The objective of Natural Selection is: all species will choose the best partner possible for what they consider to be the most desirable traits. It happens biologically, without conscious thought. Marine animals are not different! Natural selection frequently leads to speciation. Speciation: Speciation is the creation of a new species from environmental factors and/or 2 pre-existing species (hybridization). Environmental Example: Porkfish Hybrid Example: Dolphins Speciation of the Jellyfish: What is the most likely cause of the speciation of so many different types of jellyfish? Struggle for Existence Variation & Adaptation Survival of the Fittest Types of Evolution through Speciation: During divergent evolution, different species DO have a common ancestor that becomes less and less alike over time Ex. Animals with front limbs used for movement Types of Evolution through Speciation: During convergent evolution, different species do NOT have a common ancestor, they evolved separately but look similar Ex. Shark VS Ichthyosaur VS Dolphin Types of Evolution through Speciation: During divergent evolution, species have homologous traits, which look similar but have different purposes Ex. Limbs used for walking, swimming, & flying During convergent evolution, species have analogous traits, which look different, but serve the same purpose Ex. Fins, flippers, and wings used to swim Types of Evolution through Speciation: Example: Evolution of whales http://ocean.si.edu/oceanvideos/evolution-whalesanimation Did You Complete Your Exit Today? 1. Today I learned… (see learning goals!) 2. My strengths are… (be specific!) 3. My weaknesses are… (ok to have none )