Transcript Slide 1
All life has heredity in DNA A always bonds with T, and C always bonds with G. Hydrogen bonds connect the two strands of DNA. All life has heredity in DNA DNA replication – the process of making an identical copy of DNA. Must occur before a cell divides. 2 All life has heredity in DNA DNA transcription: to rewrite the DNA code in RNA as a messenger that will travel outside the nucleus to begin protein production. RNA Single stranded; sugar is ribose. A—U DNA T — A RNA G—C C—G Messenger RNA 3 All life has heredity in DNA DNA translation: the code in the messenger RNA is translated into protein within an organelle called a ribosome. Cytoplasm Nucleus Ribosome 4 Proteins Proteins are polypeptides, which are long chains of amino acids. The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up proteins. During translation, proteins are created from long chains of amino acids whose structure depends on the order of amino acid assembly. Conservation of Mass and Energy in Biological Systems Mass and energy cannot be created or destroyed but can be converted from one form to another. Energy is conserved as it flows through an ecosystem. Energy moving through an ecosystem changes from light energy to chemical to thermal and mechanical energy. All organisms respond to environmental stimuli Pathways of energy transfer Food web All life has metabolism Note units of energy here. 90% of energy is not transferred to next level. Level 4 3 2 1 Organisms occupy trophic (energy) levels in the environment. They use energy for themselves and also release heat in the process. For these reasons, only 10% of the energy is available to the next higher trophic level of the energy pyramid. 9 All organisms respond to environmental stimuli How many food chains are in this web? 10 Interdependence in Ecosystems Ecology is the study of relationships among organisms and their environment. Ecosystem is made up of all the communities in an area and the nonliving things with which they interact. When organisms rely on each other, they are interdependent. (food chain, food web, energy pyramids) Biodiversity is the variety of life in an ecosystem. (coral reefs, rain forests) Symbiosis occurs when two or more different species have a close relationship. Mutualism – both species benefit Commensalism – one species benefit and the other is not harmed or helped Parasitism – one species benefits while harming the other one. Metabolism: the sum of all the biochemical reactions in an organism All organisms require energy. 1. Autotrophs get their energy from the sun. Photoautotrophs use sunlight to make food (photosynthesis) Chemoautotrophs use chemicals such as iron & sulfur as their energy. These organisms live in the dark. 2. Heterotrophs must consume food for energy Herbivores – consume only plants Carnivores – consume only other animals (meat) Omnivores – consume both 14 3. Decomposers – break down the complex compounds of dead and decaying animals. They also break down energy into molecules that are then returned to the environment. Carbon as CO2, Nitrogen Bacterias, Fungi, vultures, maggots, hyenas… Elements Essential to Life on Earth CHON Carbon, Hydrogen, Oxygen, Nitrogen Found as part of natural cycles Glucose, water, photosynthesis, etc Natural Changes in Ecosystems An ecosystem consists of all the organisms living in an area, as well as the nonliving parts of that environment. Biotic Factors Abiotic Factors Biotic factors – living things Abiotic factors – nonliving things Limiting factors – anything that limits the ability of an organism to live in a certain place. (food, temperature, shelter) Succession – normal, gradual changes that occur in the types of species that live in an area. There are 2 types. Primary succession Ecosystems go through successions over time and will slowly return to their original climax state if disturbed. New soil must first be created in primary succession, after volcanic eruptions or ice sheets scour the earth. Secondary succession Occurs in areas that previously contained life and still contain soil. After a fire, soil remains, and a previously established ecosystem can return relatively quickly. Biomes Large regions that have similar climates and similar ecosystems Areas of land with similar environments The amount of precipitation and average temperature determine the type of biome. Refer to table 1 Natural Selection and Species Diversity Evolution is the process of change over time as a result of natural selection. Natural selection is a mechanism for change in populations. It occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. There are 3 types of natural selection: 1. Stabilizing selection – favors average individuals 2. Directional selection – favors one of the extreme variations 3. Disruptive selection – individuals with either extreme of a trait’s variation are selected for survival. A population that is in genetic equilibrium is not evolving. Any factor that affects the genes disrupts this equilibrium, which results in evolution. Mutation is a mechanism for genetic change. Environmental factors such as radiation, chemicals can cause mutations. All life must evolve (p.138) Thanks to successive mutations in their DNA and sexual reproduction, groups of organisms (not individuals) change over time in order to survive within changing environments. This is Charles Darwin’s idea of natural selection and survival of the fittest. Fossil records show that organisms with similar structures (homologous parts) trace back to a common ancestor. Mammals, birds, reptiles & amphibians trace back to fish, which go back further, eventually to bacteria. 29 Homologous structures Homologous structures indicate a common ancestor. Over time (millions of years, usually), adaptations to new environments cause bones (or beaks) to change. Analogous structures Body parts of organisms that do not have a common evolutionary origin but are similar in function.