Transcript Document
Diversity of life and common challenges to life Three Domains of Life on Earth: Archaea Eubacteria Eukaryota What are the kingdoms of Eukaryota? Protistan – Diverse, differ enormously – Have a nucleus, mitochondria and possibly chloroplasts – Sexual or asexual reproduction – Single cells to multicellular – Autotrophs or heterotrophs – May move by cilia and flagella What are the kingdoms of Eukaryota? Fungi – Bread molds, sac fungi, club fungi – Heterotrophs • Most are saprobes; obtain nutrients from nonliving organic matter • Only a few are parasites • Serve impt role in ecosystems – are vital decomposers and plant symbionts – – – – Multicellular Mycelia (branching tubular threads of hyphae) Cell walls contain chitin Reproductive structure = fruiting body = mushroom • Spores can resist dehydration • Remain dormant until environmental conditions favor germination Lichen: a composite organism A symbiosis: fungus + photosynthetic algae; what is the advantage? Fungus composes bulk of the structure Mycorrhiza – another symbiosis • Mutualism between fungi and a plants – 90% of Vascular Plant Families – Necessary for colonization of land plants? • What does fungus gets from plant? • What does plant get from fungus? with without What are the kingdoms of Eukaryota? • Protistans • Fungi • What are the other two kingdoms? Commonality of Life on Earth All organisms made of cells - single cells - integrated multi-cellular organisms with Division of labor: tissues, organs, organ systems Living organisms can compartmentalize Plant response to a wound or pathogen Walls thicken; Toxins and resins produced All living things must obtain energy from: sun and inorganic molecules = ? eating other organisms All organisms reproduce asexual – mitosis for growth, repair and for cloning self sexual – generates diversity All organisms involved in relationships with other species All organisms evolve - Land plants and land animals arose from aquatic ancestors - Both face new challenges in the drier environment - Form and internal functions are answers to these challenges All organisms eventually die and go extinct All organisms must accomplish certain tasks to maintain order, structure Move gases, water, nutrients – Internal transport- Vascular, respiratory and circulatory systems – Maintain water balance; screen toxins– kidneys, stomata, liver – Dispose of waste – complete digestive system? Defend against external threats – Predators, disease, parasites – Competition Challenges differ among habitats Physical resources vary: – Water – Nutrients – Temperature • Interpret environmental signals and adjust internal response • Maintain a stable internal environment = homeostasis – Maintaining a stable fluid environments for all living cells Three components interact to provide homeostasis Environmental cue or an activity alters a condition internally Alteration triggers a response and mediates the internal condition STIMULUS (input into the system) RECEPTOR (e.g., free nerve ending in the skin) INTEGRATOR (such as the brain) EFFECTOR (a muscle or a gland) RESPONSE (system’s output) RESPONSE to the stimulus leads to change. The change is “fed back” to the receptor. In negative feedback, the response cancels or counteracts the original stimulus. Example of negative Feedback - Body temperature regulation: 1) Body temp rises b/c of sunshine internal conditions in body change breath harder, blood vessels dilate, sweat glands secrete more less metabolic heat is retained body temp drops 2) Body temp falls muscles shiver, blood shunted to interior of body, more metabolic heat produced body temp rises Positive Feedback • External or internal cue alters internal environment • The alteration triggers a response • The response intensifies the change in the internal condition – Example: childbirth: pressure on uterine wall production of oxytocin uterine muscles contract more pressure on uterine wall more oxytocin produced etc. until fetus is ‘born’