Ancient Reducing Atmosphere Oparin and Haldane proposed that Earths ancient atmosphere was reducing rather than oxidizing. Why was there no free oxygen in Earths early atmosphere? Why would the first life not evolve in an oxidizing atmosphere? P 494 Miller and Urey simulated Earths early atmosphere electricity simulated lightning Why did they use uV light? Miller and Urey simulated Earths early atmosphere electricity simulated lightning Why did they use uV light? An alternate atmosphere contained carbon monoxide, carbon dioxide, nitrogen gas and water vapor Experiments have produce all 20 amino acids, sugars, lipids, purines, pyrimidines What is the importance of amino acids? What is the importance of nucleic acids? Archaea live in extreme environments and have cell walls with no peptidoglycan Formerly eubacteria Most bacteria range from 1- 5 um while eukaryotes range from um Simple cell wall with relatively large amounts of peptidoglycan Penicillin prevents crosslinking in the peptidoglycan and prevents the formation of a functional cell wall Simple cell wall with relatively large amounts of peptidoglycan Penicillin prevents crosslinking in the peptidoglycan and prevents the formation of a functional cell wall More complex cell wall with less peptidoglycan but with an outer membrane with lipopolysaccharides -carbohydrates bonded to lipids Nitrosomonas Pseudomonas Rhizobia Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Under one evolutionary scenario, the endomembrane system of eukaryotes (nuclear envelope, endoplasmic reticulum, Golgi apparatus, and related structures) may have evolved from infoldings of plasma membrane. Another process, called endosymbiosis, probably led to mitochondria, plastids, and perhaps other eukaryotic features. Fig. 28.4 Formation of Chloroplast cyanobacteria green algae green plants Problems Aquatic Plants Face in a Terrestrial Environment Obtaining enough water transporting water and dissolved substances from restricted areas of intake to other areas Preventing desiccation Maintaining enough moist surface area for gas exchange carry out reproduction in an environment where sperm, zygote and embryo will dry out withstanding extreme fluctuations in environment Supporting a large plant body against gravity Four Major Groups Adaptations of Bryophytes form embryophytes Gametes develop within gametangia anthridium archegonium Spores with walls of sporopollenin cuticle stomata alternation of generations the haploid gametophyte is the dominant generation Bryophytes, pteridiophytes, gymnosperms, ands angiosperms demonstrate four great episodes in the evolution of land plants: 1.the origin of bryophytes from algal ancestors 2.the origin of vascular plants and their diversification 3.the origin of seeds 4.the evolution of flowers Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 29.1 Homologies between Charophytes and Plants Homologous chloroplasts chlorophyll b, beta- carotene thylakoids as grana DNA Biochemical similarity cellulose cell walls (rosette cellulose- synthesizing complexes) matching enzymes within peroxisomes Similar mitosis and cytokinesis dissapearance of nuclear envelope spindle remains till cytokinesis Cell plate formation similar sperm similar genes and rRNA The elongation and branching of the shoots and roots maximize their exposure to environmental resources. This growth is sustained by apical meristems, localized regions of cell division at the tips of shoots and roots. Cells produced by meristems differentiate into various tissues, including surface epidermis and internal tissues. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 29.3 Most ferns are homosporous The gametophyte is bisexual producing both sperm and eggs In pteridophytes, gymnosperms, and angiosperms, the sporophyte is the dominant generation. For example, the fern plant that we typically see is the diploid sporophyte, while the gametophyte is a tiny plant on the forest floor. The stomata is an adaptation to let in carbon dioxide into the leaf The cuticle is a secondary product produced on the surface of leaves to prevent dessication Xylem Phloem Adaptations to Terrestrial Life Stomata p582 Cuticle p581 lignin Sporopollenin p580 gametangia p581 embryophytes vascular tissue p582 seeds flowers Adaptation of Vascular Plants Root systems absorbs water and minerals Aerial shoot systems and leaves for photosynthesis Conducting tissue xylem and phloem Lignin to strengthen and support cellulose cell walls Sporophyte is the dominant stage Branching in Sporangia increases the # of spores Most ferns are homosporous The gametophyte is bisexual producing both sperm and eggs Microscopic gametophytes of seed plants are even more reduced than those of seedless vascular plants such as ferns An ovule consists of integuments, megaspore, and megasporangium. A female gametophyte develops inside a megaspore and produces one or more egg cells. A fertilized egg develops into a sporophyte embryo. The whole ovule develops into a seed. Fig. 30.2 There are four plant phyla grouped as gymnosperms. 2. The four phyla of extant gymnosperms are ginko, cycads, gnetophytes, and conifers Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 30.4 Gymnosperm only have tracheids - no vessels Vessels form contiunous tubes and thus are more specialized for transport of water and less for support. The thick lignified xylem cell helps in support Monocot one embryonic leaf - cotyledon does not have vascular cambium and secondary growth scattered vascular bundles leaves have parallel venation no petioles flower parts in multiples of three Monocot one embryonic leaf - cotyledon does not have vascular cambium and secondary growth scattered vascular bundles leaves have parallel venation no petioles flower parts in multiples of three Dicot two embryonic leaves - cotyledons has vascular cambium and secondary growth vascular tissue arranged in circular bundles leaves have netted venation has petioles flower parts in multiples of four or five Dicot two embryonic leaves - cotyledons has vascular cambium and secondary growth vascular tissue arranged in circular bundles leaves have netted venation has petioles flower parts in multiples of four or five Refinements in vascular tissue, especially xylem, probably played a role in the enormous success of angiosperms in diverse terrestrial habitats. Like gymnosperms, angiosperms have long, tapered tracheids that function for support and water transport. Angiosperms also have fibers cells, specialized for support, and vessel elements (in most angiosperms) that develop into xylem vessels for efficient water transport. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig A flower is a specialized shoot with four circles of modified leaves: sepals, petals, stamens, and carpals. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig a The life cycle of an angiosperm begins with the formation of a mature flower on a sporophyte plant and culminates in a germinating seed. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig A fruit is a mature ovary. As seeds develop from ovules after fertilization, the wall of the ovary thickens to form the fruit. Fruits protect dormant seeds and/or aid in their dispersal. 3. Fruits help disperse the seeds of angiosperms Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Fungi are heterotrophs that acquire their nutrients by absorption. They absorb small organic molecules from the surrounding medium. Exoenzymes, powerful hydrolytic enzymes secreted by the fungus, digest food outside its body to simpler compounds that the fungus can absorb and use. Extracellular digestion. 1. Absorptive nutrition enables fungi to live as decomposers and symbionts Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings The vegetative bodies of most fungi are constructed of tiny filaments called hyphae that form an interwoven mat called a mycelium. 2. Extensive surface area and rapid growth adapt fungi for absorptive nutrition Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 31.1 More than 100,000 species of fungi are known and mycologists estimate that there are actually about 1.5 million species worldwide. Molecular analyses supports the division of the fungi into four phyla. Introduction Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 31.4 The four fungal phyla can be distinguished by their reproductive features. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings The fungal hyphae provides most of the lichens mass and gives it its overall shape and structure. The algal component usually occupies an inner layer below the lichen surface. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Mycorrhizae are mutualistic associations of plant roots and fungi. The anatomy of this symbiosis depends on the type of fungus. The extensions of the fungal mycelium from the mycorrhizae greatly increases the absorptive surface of the plant roots. The fungus provides minerals from the soil for the plant, and the plant provides organic nutrients. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig (3) The Bilateria can be divided by the presence or absence of a body cavity (a fluid-filled space separating the digestive tract from the outer body wall) and by the structure the body cavity. Acoelomates (the phylum Platyhelminthes) have a solid body and lack a body cavity. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 32.6a In some organisms, there is a body cavity, but it is not completely lined by mesoderm. This is termed a pseudocoelom. These pseudocoelomates include the rotifers (phylum Rotifera) and the roundworms (phylum Nematoda). Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 32.6b Coelomates are organisms with a true coelom, a fluid-filled body cavity completely lined by mesoderm. The inner and outer layers of tissue that surround the cavity connect dorsally and ventrally to form mesenteries, which suspend the internal organs. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 32.6b Many protostomes undergo spiral cleavage, in which planes of cell division are diagonal to the vertical axis of the embryo. Some protostomes also show determinate cleavage where the fate of each embryonic cell is determined early in development. The zygotes of many deuterostomes undergo radial cleavage in which the cleavage planes are parallel or perpendicular to the vertical egg axis. Most deuterostomes show indeterminate cleavage whereby each cell in the early embryo retains the capacity to develop into a complete embryo. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings