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The Tree of Life...
Transcript of The Tree of Life...
All species originally originated from a common ancestor. All domains of life also sprung from this single common ancestor, which is believed to be singular celled organisms first classified to be living things.
So what are Bacteria?
Bacteria and Reproduction...
These creatures reproduce asexually through a process called binary fission, and can maintain genetic diversity by taking up DNA from other Bacteria. A process known as transformation.
Types of Bacteria...
Some of the major groups (phylum) of Bacteria are Proteobacteria, Spirochaetes, Actinobacteria and Cyanobacteria. Bacteria can be identified either as Gram-positive or gram-negative.
Domain Bacteria corresponds with kingdom Eubacteria, they are unicellular and prokaryotic. They have thick cell walls made of peptidoglycan. Bacteria can have spherical (cocci), rod like (bacilli), or spiral (spirilla) body shapes.
What are Archaea?
Members of domain Archaea live in extreme environments, such as brine pools, hot springs and the stratosphere. They are unicellular and prokaryotic, domain Archaea corresponds with kingdom Archaebacteria.
Archaea are more closely related to Eukaryotes than bacteria, they lack cell walls of peptidoglycan. These organisms structures are similar to those of Bacteria, except the differences in their components.
The main clades...
Genetic organization and reproduction processes are similar to those of Bacteria. There are four main clades in kingdom Archaebacteria, Crenarchaeotes (thrive in hot and acidic environments), Korarchaeotes (least-evolved organisms), Nanoarchaeotes (smallest genome of any organisms) and Euryarchaeotes (found in oxygen-poor environments).
More to uncover...
Many Archaea are obligated anaerobes, and while some may live in extreme environments other Archaea have been found in more moderate habitats, plankton at sea for example.
This kingdom is a paraphyletic group where its members have no common ancestor. Protists are generally single celled eukaryotes, these is a great diversity in structure and organelles from chloroplasts to mitochondria.
They can move by using cilias, pseudopods, or flagella. Most have sexual phases in their lifecycle and can change phases through he alternation of generations process. Reproduction occurs both sexually or asexually, some of them are also capable of conjugation.
Protists can be autotrophic and heterotrophic; some exists as muralists or parasites to other creatures. There are six major clades of Protista. Excavates (possess feeding grooves supported by microtubules). Chromalveolates (includes Brown algae, Golden algae, and Dinoflagellates). Cercozoa, Foraminiferans and Radiolarians (These three are classified into one clade based on molecular analysis, typically members of this clade have cytoplasmic projections called pseudopods or protective shells).
The other three phylum are Rhodophytes (also known as Red algae, close to Kingdom Plantae), Amoebozoa (move by use of pseudopods), and Choanozoa (found in aquatic environments and close to kingdom Animalia).
Watch the video to learn more!
Watch this video to learn more!
There are four major phylums of Fungi, Basidiomycetes (fruiting body that resemble a club, associated with mushrooms, earthstars, jelly fungi, rusts), Ascomycetes (have sac like reproductive structure which contains spores), Zygomycetes (generally lack cross walls between cells) and Chytrids (most species are decomposers, only fungi with flagellated spores).
Asexual reproduction includes budding, splitting, or dispersing spores. Sexual reproduction involves “+” and “-“ hyphae meeting to produce a sporangium from a diploid zygospore.
Fungi obtain nourishment by using digestive enzymes to break organic matter into molecules so they can absorb the nutrients. Like Protists, Fungi undergo alternation of generations between being haploid or diploid.
Fungi are heterotrophic eukaryotes with cell walls containing chitin; they are more closely related to Kingdom Animalia than Plantae. Unicellular Fungi include yeasts, while others have a multicellular body called mycelium, branching filaments called hyphae and a fruiting body that grows from the mycelium.
Fungi may form relationships with other organisms; such relationships include parasitism or more well known mutualistic relationships (Lichens and Mycorrhizae).
Where is bacteria DNA located?
Unlike Eukaryotes, Bacteria do not have a nucleus and all DNA are contained within one DNA double helix with a closed loop. Smaller sections of DNA that can undergo conjugation are assembled as plasmids.
Intro to Plants!
Kingdom Plantae is composed of plants, these organisms are eukaryotes with cell walls contain cellulose and carry out photosynthesis using chlorophyll a and b. They store products of photosynthesis as starch.
Most plants are autotrophs or partial heterotrophs; a few are parasites or saprobes. Plants need sunlight, water, minerals, and gas exchange to survive.
Plants also undergo alternation of generations; the diploid phase is known as the sporophyte while the haploid phase is known as the gametophyte. As plants develop along the route of evolution, the sporophyte stage gains dominance.
There are five major evolutionary stages to plants, the first being green algae, the second embryo formation, the third is development of vascular tissue, fourth is zygote contained within seeds, the fifth is flowers as reproductive organs and seeds being enclosed in fruit.
The Five Major Plant Phylums
Bryophytes are among first plants to get established on land. They have specialized reproductive organs enclosed by nonproductive cells. This clade includes mosses (waxy coating to resist drying, thin filaments known as rhizoids extending into soil absorbing minerals and water), hornworts, and liverworts.
Bryophytes have no vascular tissue (tubes hardened by lignin), thus are small and cannot easily carry water. They are often called non-vascular plants. Bryophytes have gametophyte as the dominant stage in their life cycle.
The gametophyte stage carries out most of plants’ photosynthesis, the sporophyte depends on gametophyte for nutrients. Sporophytes generally have sporangium to spread haploid spores. Flagellated sperm produced by antheridia swim in water toward an archegonia. Some species can produce both sperm and egg.
Watch the video to learn more!
Tracheophytes contain vascular tissue but not seeds, thus allowing plants to grow higher above the ground and carry nutrients and water more efficiently. They have specialized cells called tracheids (hollow, tube-like, with think cell walls strengthened by lignin).
Trachied ells are stacked one upon the other, there are openings between cells (pits) to allow water to move efficiently through plan body by diffusion. Second transport tissue called phloem transports solutions of nutrients and carbohydrates from photosynthesis, works similar to xylem.
All seed-bearing plants are Tracheophytes. Some seedless vascular plants are club mosses, horsetails, and ferns (vascular tissues, roots, stems called rhizomes, leaves called fronds, can thrive in damp limited exposure areas).
The sporophyte stage is dominant phase in Tracheophytes life cycle. Gametophyte develops independently and follows similar process to bryophyte sexual reproduction. Once eggs are fertilized and zygote forms, typically new sporophyte grows from gametophyte
A fern's life cycle!
Seed-bearing plants in general:
Seeds appeared about 360 million years ago. Seed ferns and gymnosperms (e.g. pine trees) were dominant at first. Angiosperms (flowering plants) arose later.
Seed-bearing plants transfer gametes through exterior factors such animals and natural elements,seeds are developed to protect the embryos contained inside. The plant embryo within a seed is diploid (developmental stage of sporophyte).
Male gametophytes are contained in tiny structures called pollen grains. Zygotes within seeds grow into tiny plants, but stops while still contained inside seeds until they reach a favourable environment.
The seed coat helps protect embryo from drying out and other harsh environmental conditions. When conditions are advantageous embryo continues to grow until it pops out of the seed, if not, the seed continues to consume nutrients stored inside the seed.
Gymnosperms are called plants with "naked seeds". This means the seeds don't form inside an ovary (as they do in the angiosperms). There are four groups, the Conifers , the Cycads, the Ginkgos, and the Gnetophytes. Gymnosperms are the first true seed bearing plants, they bear seeds on the scales of cones.
Male cones produce male gametophytes, female cones female gametophytes. Male and female gametophytes grow on sporophyte. Female cones bear seeds on inside surfaces of scales. Cones are produced by mature sporophyte plant, two types of cones (pollen cones: produces pollen grains, each grain is the entire male gametophyte stage of lifecycle) and (seed cones: produce female gametophytes, near base of scales are two ovules). A conifer reproduction life cycle is two years.
The four groups of gymnosperms are known today include Conifers (pines, spruce, fir), Cycads (grows in tropical regions), Ginkgoes (common when dinosaurs were alive), and Gnetophytes (reproductive scales clustered in cones).
Gymnosperms are seed-bearing vascular plants with seeds enclosed in a scale rather than fruit. Adults are stationary while gametophytes are motile by environmental influences. This phyla have true vascular tissue and reproduction can only be sexual through fertilization.
Once pollen grain reaches ovule, the grain splits and change into a pollen tube. When the pollen tube reaches to female gametophyte, one nuclei dissolves leaving other sperm cell to fertilize egg inside female gametophyte. Fertilization produces diploid zygote, embryo, which is then encased as a seed. Seeds disperses by wind to form new sporophyte plant.
What are Angiosperms?
Angiosperms account for vast majority of plant species today. Angiosperm plants bear seeds in a closed ovary, ovaries are part of reproductive organs known as flowers, flower ovaries surround and protect seeds.
Adult plants are stationary while male gametophytes can be transported either by animals or natural factors. Angiosperms contain true vascular tissue, and reproduce sexually by flowers, after fertilization ovaries within flowers develop into fruits to protect seeds. Most species of flower bearing plants have both male and female reproductive gametophytes within each organism; some species have only a single gender.
Flowering plants are often classified as either monocots or dicots based on their cotyledons, they are also categorized by their life cycle (Annual, Biennial, or Perennial), as well as their differences in stems, which could be woody or herbaceous.
Male gametophytes (pollen grains) develop in anthers. Each spore undergoes one mitotic division to produce two haploid nuclei for each pollen grain. Female gametophytes develops inside carpel, ovules is enveloped by the ovary (future fruit). A single ovule makes up a female gametophyte. Cell walls form around six of the ovules, one of the eight is the nucleus of the egg (female gamete), and if fertilization takes place this egg will fuse with sperm to produce a zygote.
Once pollen grain lands on stigma it grows a pollen tube. When pollen tube reaches ovule, two fertilizations takes place. One, sperm fuses with egg nucleus to form diploid zygote, the other fuses with two polar nuclei to form a triploid cell that will grow into a food rich tissue called endosperm that nourishes the seedling. Seed is then made into an embryo.
Clades within this phylum include: Amborella (only found in New Caledonia), Water Lily (50 species known today), Magnoliids (includes laurels and tulips), Monotcots (many species known in agriculture) and Eudicots (75% of all angiosperm species).
Green algae are assumed to be similar the earliest plants on earth. They are mostly unicellular though there are some multicellular species, organisms in this phylum make no embryos or specialized tissues, and are primarily aquatic. Most of these single celled creatures form colonies that appear to be branching filaments or pods containing groups of individuals.
Many swim with a whip like flagella, and thus need water for sexual reproduction in order for two gametes to meet. Unlike other types of plants, chlorophyta do not go through alternation of generations in every lifecycle as they typically prefer to reproduce asexually, unless conditions are unfavorable. The three most diverse clades of green algae include classic green algae (found in both fresh and salt water), Ulvophytes (Seaweed) and Charophytes (stoneworts).
So what are animals?
Animals are multicellular, heterotrophic, eukaryotic organisms whose cells lack cell walls and instead have cell membranes; 95% of animals are invertebrates and only 5% are chordates. Typical animal structures are based on levels of organization, body symmetry, differentiation of germ layers, body cavities, patterns of embryological development, segmentation, cephalization and limb formation; there are exceptions such as sponges.
Body systems work together in animals to maintain homeostasis. Animals may obtain food through a variety of methods; species could use intracellular and extracellular digestion, or sometimes both. Some animals are filter feeders, detritivores, carnivores or herbivores. Depending on species, animals can reproduce asexually or sexually, or sometimes alternate between phases of the two methods of reproduction.
Animals are defined according to adult body plans and patterns of embryological development. In total there are nine phylums to Kingdom Animalia. Porifera, Cnidaria, Arthropoda, Nematoda, Platyhelminthes, Annelida, Mollusca, Echinodermata, and Chordata.
Sponges are the simplest animals. They live in aquatic environments and most are filter feeders (intracellular digestion). Respiration occurs via oxygen diffused from flow of water through body. Sponges have no nervous system, and while juveniles could sometimes drift or swim, adults are stationary. Reproduction could happen sexually with dispersal of sperms.
The group consists of approximately 15,000 extant species in three distinct groups, which include: Hexactinellida (Glass sponges), Calcarea (Calcareous sponges) and Demospongiae (Typical Sponges). They are classified as animals because they are multicellular, heterotrophic, lack cell walls, and have specialized cells.
Sponges have no true tissues and organs, their internal skeletons are composed of sponging or spicules composed of either calcium carbonate or silica. Sponges also have no body symmetry and can be found in a variety of shapes and sizes.
Cnidarians are the simplest animals to have specialized tissues and body symmetry, they are aquatic and most are carnivorous. Respiration is done by diffusion through body walls; cellular wastes are also forsaken in a similar manner. Contain specialized sensory cells such as eyespots to detect light.
Movement varies from stationary to jet propulsions created from muscle contractions. Reproduction is an alternation between sexual and asexual. As carnivores, Cnidarians are predators; digestion of food is a mixture of intra and extracellular processes. Clades of the Cnidaria phylum include Hydrozoa, Anthozoa and Scyphozoa.
Arthropods include a wide diversity of organisms, all multicellular. They possess segmented bodies and jointed appendages, supported by exoskeletons made of chitin, which is periodically shed. These organisms are coelomate protostomes with bilateral symmetry. Individual species can respire terrestrially, aquatically, or a combined mixture.
Usually Arthropods reproduce sexually, through some could do asexual reproduction. Many undergo metamorphosis in development. Arthropods have multifaceted diverse methods of feeding and digestion, each unique to their own species. A few of the most well known clades of Arthropods are Crustacea (ex. lobsters), Arachnida (ex. tarantulas) and Insecta (ex. Beetles).
Nematodes are also known as roundworms. They are
unsegmented worms with a tough outer cuticle. These organisms have a straightforward digestive system where food passes from mouth to anus. Some are predators, some parasites, and others are decomposers.
Circulation occurs through diffusion, similar to respiration and the process of getting rid of waste, both which happens through body walls. Their muscles work like hydrostatic skeleton, allowing them to move like water snakes. Nematodes reproduce sexually; parasites lay eggs inside of hosts. Roundworms live in almost every habitat conceivable. There are more than 15,000 known species of roundworms.
Platyhelminthes, also known as flatworms, are acoelomates. They have soft tissues and internal structures. These organisms are the simplest animals to have three embryonic germ layers, bilateral symmetry, and cephalization. Some have brilliant colors and patterns. Flatworms have three categories of digestion and feeding, free-living organisms (Turbellaria) tend to be predators or scavengers, parasitic organisms (Trematoda) feed on their host, and tapeworms (Cestoda) absorb nutrients from the food intake of its host that have already been digested.
Circulation and respiration both occurs through diffusion and most release waste from pores in the skin. Platyhelminthes possess specialized sensory cells, and depending on the species, move by either using cilia or muscle cells. Free-living Platyhelminthes reproduce sexually while parasites can reproduce sexually or asexually.
Annelids, also known as segmented worms, are coelomate protostome worms with segments separated by internal partitions. Some are filter feeders, carnivores, or parasites, digestive structures and systems are diversified. Circulatory system is closed with dorsal and ventral blood vessels. Respiration in aquatic environments involves gills and on terrestrial environment, skin.
Mollusks have soft bodies and, usually, a muscular appendage as well. Body forms vary depending on organism. These creatures are coelomate protostomes with bilateral symmetry. This phylum have an assortment of feeding styles; some species are carnivores, herbivores, filter feeders, detritivores, or parasites. Circulatory systems could be closed or open depending on species.
These organisms contain a rudimentary brain and few nerve cords, they also have a hydrostatic skeleton and muscle cells for movement. Reproduction occurs sexually. Well-known groups of Annelids include Hirudinea, Polychaeta and Oligochaeta.
The complexity of nervous systems and movement methods also vary greatly depending on organism. Reproduction occurs sexually; most aquatic species have an individual trochophore larva stage. Three major categories of Mollusca are Bivalvia (Ex. Giant clams), Gastropoda (Ex. Snails) and Cephalopoda (Ex. Octopi).
Echinoderms are coelomate deuterostomes. These organisms are marine animals with spine skin surrounding an endoskeleton, they have a water vascular system with suction cup like ends used for movement and feeding. Body structures have a 5-part circular symmetry. Echinoderms can be filter feeders, detritivores, herbivores, or carnivores depending on group. Respiration occurs through surfaces of tube feet or skin gills.
Digestive wastes are released through the anus, while cellular wastes are discharged as ammonia through respiratory systems. Most of these organisms have scattered sensory cells that detect light, gravity, and by various means, prey. For movement, endoskeleton permits locomotion with tube feet. Reproduction occurs sexually. Classes of Echinoderms include Crinoidea, Asteroidea, Echinoidea, Ophiuroidea and Holothuroidea.
The Phylum Chordata includes the well-known vertebrates (fishes, amphibians, reptiles, birds, and mammals), it is mostly composed of animals with a vertebral column, through there are also invertebrate chordates. All chordates exhibit four characteristics during at least one stage of life: a dorsal, hollow nerve cord; a tail that extends beyond the anus; a notochord; and pharyngeal pouches.
Nonvertebrate chordates are coelomate deuterostomes. They are species that lack a vertebral column but still possess all the other characteristics that distinguishes chordates. They are typically filter feeders, circulatory system pumps blood but have no central organ like a heart, gas exchange occurs through body surfaces or gills, sensory organs usually include some specialized organs, cells and eyespots for light detection. During larvae stage (Tunicates) they are capable of movement but are stationary as adults. Reproduction occurs sexually or through budding of cells. There are two major groups of nonvertebrate chordates, Cephalochordata (Lancelets) and Urochordata (Tunicates).
Chordates with a vertebral column divides into five major groups, fishes, amphibians, reptiles, birds, and mammals. Fishes are aquatic vertebrates, adapted to life in water. Feeding methods varies widely, some are herbivores, carnivores, parasites, filter feeders, detritivores and more. Circulation is single looped, specialized respiration organs include gills. Fishes have a brain and developed sense organs, movement is propelled by paired muscles on either side of backbone. Reproduction may occur through external or internal fertilization.
Most amphibians live two stages in life, one as larvae and another as an adult. Larvae tend to be filter feeders or herbivores, adults are usually carnivores. Circulation is a double loop system with a three chambered heart. Respiration occurs either through gills, lungs, or other apparatuses. Amphibians have a well developed nervous and sensory system. As larvae, most species have tails, as adults some have specialized limbs for climbing. Reproduction is sexual and females lay eggs that hatch into larvae.
Reptilia & Birds
Mammals are endothermic vertebrates with hair (there are exceptions) and mammary glands which produce milk to nurture their young. Diet is varied but most species are either herbivores or carnivores. Mammals have a four chambered heart and lungs are controlled by muscles. Class mammalia have the most highly developed brain with keen senses. There is a wide variety of movement for class mammalia, fertilization happens internally and babies are born alive. Some orders of mammalia are: Monotremata, Marsupialia, Sirenia, Carnivora, Cetacea, Primates and many more.
Classes of Chordata
Class Reptilia are ectothermic vertebrates, it includes living reptiles, extinct dinosaurs, and birds (descendants of one dinosaur group). Feeding methods vary depending on species, herbivores have long digestive systems and carnivores tend to swallow prey whole. Respiration is operated by spongy lungs for gas exchange. Brain is well developed and may include special sensory organs such as infrared detectors. Most have limbs for movement (exception: snakes). Embryos are contained in eggs. Groups of reptiles include: Sphenodonta, Squamata, Archosaurs, and Testudine.
Birds can be considered to be endothermic reptiles with feathers and hard-shelled amniotic eggs. They uses bills to digest food and can have a varied diet. Their respiration patterns supports their high metabolic rates. Birds have highly developed sensory organs, their skeletons are light with hollow bones. There are many groups of birds.
Biology Project ~ Nina Zhang
What are viruses?
Viruses are non-living particles that contain nucleic acids and have the ability to infect living cells. Viruses are much smaller than normal cells, unlike cells they do not reproduce or use energy. However, viruses can evolve and create other viruses through infection. Besides nucleic acid, viruses have a protein coat called a capsid and a lipid membrane.
Reproduce through infection...
Viruses make other viruses by infecting other cells. They contaminate a cell by inserting their genetic material into the cell to replicate copies of themselves. There are two types of viral infections. A lytic infection is where once the viral genes are transcribed into the host cell the cell immediately begins to make viral proteins and components. The other is a lysogenic infection, where the viral DNA may lay dormant in the host cell, called a prophage, and is even copied along with the host's DNA. However, once conditions are met the lysogenic infection becomes a active lytic infection. In both cases, the host cell eventually fills with viruses and breaks apart, releasing more virus particles.
A retroviruses is a group of RNA viruses (ex. HIV), these viruses have their genetic info copied from RNA to DNA. The basis of virus is that they use the cellular machinery of their hosts to reproduce. Essentially, viruses are parasites. There is no perfect way to cure a viral infection, though a infection could be prevented by vaccines.