Biology 2201 Unit 2 Chapter 6: Plants and Animals Name: 1
Kingdom Plantae (Plants) 164-181: Botany is the study of plants. All plants are said to have a common ancestor; (ie.) it is thought that plants have evolved from an ancient group of green algae. Plants and green algae share a common evolutionary ancestry. The general characteristics of plants are the following: Photosynthesis ability to absorb water and nutrients ability to conserve water and reduce the drying effect of air process of gas exchange presence of supporting tissue ability to reproduce Plants can be classified according to the presence or absence of vascular tissue. Vascular tissue is the tissue that supports water and the products of photosynthesis throughout a plant. A plant s vascular system has a similar function to the circulatory system that carries blood throughout our bodies. It transports water, dissolved minerals and sugars to all parts of plants. This feature helps to divide the plant kingdom into two major groups: Plants lacking vascular tissue are called bryophytes. (non- vascular plants) Plants which have vascular tissue are called tracheophytes. (vascular plants) Vascular tissue is made up of xylem and phloem cells. Xylem carries water and minerals to the leaves of plants. Phloem transports food synthesized in leaves throughout the plant. Land plants have a cuticle and stomata (singular = stoma) present. A cuticle is a noncellular layer secreted by epidermal cells which helps to protect cells from drying out. Stomata are pores in the epidermis of a plant, particularly the leaves, which permit the exchange of gases between the plant and the air around it. Classification system (land plants): 1. Nonvascular (Bryophytes) (eg.) mosses, liverworts, hornworts 2. Vascular (Tracheophytes) 2a. Seedless (Spores): (Spore-bearing plants) (eg.) whiskferns, club mosses, horesetails, ferns 2b. Seed (embryo + stored food + tough water proof coat or seed coat) Gymnosperms (cone-bearing plants): conifers. 2
2c. Angiosperms (flowering plants): classified into two groups according to number of seed leaves or cotyledons on the embryo within the seed monocots (one seed leaf) and dicots (two seed leaves). 1. Nonvascular Plants: BRYOPHYTES (Phylum Bryophyta): Bryophytes are nonvascular land plants that are small in size and grow close to the ground. Examples would be mosses, liverworts and hornworts. They reproduce by alternation of generations; a two part life cycle with alternating monoploid (n) and diploid (2n) phases. For bryophytes, the dominant part of the life cycle is the gametophyte generation (what is actually seen). (See Figure 6.3, p. 166). Characteristics of Nonvascular: 1. They lack specialized tissue that transports water as in vascular plants. There is a problem of dessication or drying out in these plants. 2. They lack true roots, stems and leaves and are anchored to the ground by structures called rhizoids. A rhizoid is a simple structure (other than a true root) which doesn t channel water to other parts of the plant. 3. They require water for sexual reproduction. Water is needed for fertilization to occur. Sperm must swim through water in order to reach the egg. 2. Vascular Plants TRACHEOPHYTES (Phylum Tracheophyta): Tracheophytes are true terrestrial plants. Examples would be ferns, herbs, shrubs, trees and flowering plants. They are vascular plants and have vascular tissue. These are modern-day plants and the sporophyte generation is predominant. Some tracheophytes are spore-producing vascular plants; such as whiskferns, club mosses, horesetails and ferns. Characteristics of vascular plants: 1. They are vascular plants having specialized conducting tissue; xylem (water) and phloem (food). 2. Means of reproduction: spores - club mosses, horsetails, ferns seeds - flowering plants, conifers (Note: All spore bearing vascular plants require water, which reflects their aquatic ancestry.) 3
3. Dominant phase in the life cycle is the sporophyte generation (larger than gametophyte); gametophyte generation is very small, only mm in length. (Note: This is an evolutionary trend.) 4. Evolution of the reproductive cycle is such that water is not an essential requirement for reproduction. It enables plants to survive in a terrestrial environment. This allows for greater adaptability and less dependence on a wet environment (like the bryophytes). Diversity and success of the Angiosperms: The angiosperms are the flowering plants and are the most diverse plant group. This diversity is due to a variety of factors, such as: 1) the assistance of animals and wind in pollination; 2) the presence of structures in plants specific to attracting certain animal pollinators whom the plants supply with food; 3) the way seeds are protected; 4) the function of fruits in seed dispersal, and 5) the presence of specialized tissues in plants to help them survive heat, cold, and droughts. Explanation of the key factors: 1. Assistance of animals and wind in pollination. Diagram Pg. 176 Pollination is the process by which pollen reaches the stigma or the transfer of pollen to female reproductive structures of a plant. The agents of pollination would be animals, wind and flower structure. Animals such as bees, bats, birds, butterflies, etc. are able to move from one flower to another and are known as pollinators. Animals move from plant to plant in search of a sugary food called nectar. The animals will usually use a specific flower. Flower colour, odour, size and shape are related to the specific pollinators of the plant. For example, butterflies and moths have long sucking mouth parts. Therefore, certain plants evolved structures that have petals which form a long tube with the nectar at the base. In this way, only certain insects can pollinate the plant. This parallel evolution of plants and pollinators was a major factor in the domination of flowering plants on the earth; (ie). pollinators are specific. Pollination by wind is very inefficient and therefore plants produce large amounts of pollen. Almost all of the pollen falls within 100 m of the parent plant. This means that this is only good within a large population which grows close together. The characteristics of plants pollinated by wind would be: - flowers are small and grow in clusters - drab colour, odourless, no nectar - petals absent or small 4
- stamen is exposed, pollen easily catches wind - feathery stigmas also increase the amount of pollen which is caught by the wind (eg.) grasses, trees such as oak, maple and birch Some plants don t need a pollinator. Pollen from the anther fertilizes egg in the same flower. This is called self - fertilization. It is very uncommon. In some plants, the pollen grains and the ovules mature at different times making self - fertilization impossible. 2. Structures present specific to attract pollinators. Flowering plants attract pollinators by supplying them with food. How a pollinator distinguishes a plant? This can be done by sighting the plant or by detecting an odour. Bees cannot distinguish the colour red and therefore are not usually found around red flowers but those with blue and yellow flowers. Some plants also have patterns or stripes which lead bees to nectar. Some flowers can produce sweet smelling scents. For example, there are some flowers that smell like decaying meat; (eg). skunk cabbage attracts flies. Hummingbirds have a poor sense of smell and therefore pollinate flowers which have little smell. Beetles usually pollinate white or dull coloured flowers with have strong odours. 3. Seed protection. Flowers are diploid sporophytes and do not produce spores. Fertilization will produce a diploid sporophyte embryo. The embryo is enclosed in hard tissue to form a seed. The seed case or hard tissue enables the embryonic plant to survive adverse weather conditions such as drought, hot or arid periods and cold. 4. Fruits have a function in seed dispersal. The fruit or fleshy walls of the ovary is another means of seed protection. Some seeds in fruits are easily dispersed by wind and by water. Some fruits are eaten and dispersed by animals. The seed resist digestion and will pass intact in an animal s feces to germinate in a new spot. 5. Specialized tissues for survival. Angiosperms have a specialized leaf structure; such as sunken stomata which helps reduce water loss. Some angiosperms have small leaf hairs which also help to reduce water loss. The most important structure for survival is the reproductive organ, the flower; the female reproductive organ is the pistil (or carpel) and the male reproductive organ is the stamen. 5
Example of the Fern Life Cycle as a representative (seedless) plant: (See Figure 6.9, p. 173). 1. A sporangium produces haploid (monoploid) spores that germinate to form a gametophyte called a prothallus. Juvenile form 2. The prothallus produces antheridia (male organs) and archegonia (female organs). 3. Sperm swim through a droplet of water to an egg produced by the archegonium. 4. The fertilized egg begins to grow into a sporophyte. Adult form 5. The sporophyte matures and roots and fronds (leaf structure) develop out of the growing rhizome. 6. Sori (brown spores) develop on the pinnae (underside of frond). Spores are formed in the sori by meiosis. ** Table # 2 : Plants 6
Kingdom Animalia (Animals): Zoology is the study of animals. Animals are multicellular and eukaryotic. Animals consume organic materials and digest it and are termed heterotrophs. Most animals are motile at some time in their lives through some simple forms are attached to a substrate (sessile). Many animals have tissues specialized for specific functions (nerve tissue, muscle). Many lower forms have simple asexual and sexual reproduction while higher forms reproduce sexually exclusively. There are two main types of animals, vertebrates and invertebrates. A vertebrate has a backbone while an invertebrate has no backbone (no bones at all usually!!!) Characteristics of Various Animal Phyla: A. body organization (cells organized into tissues, organs and organ systems). Covered in Unit 1. B. number of germ layers (tissues from which more specialized tissues develop) C. body symmetry D. a complete or incomplete digestive tract E. development (or not) of an internal cavity called a coelom B. Number of Germ Layers: Animal development depends on cell layers or germ layers. Layers: 1. Endoderm is inner layer of cells. It gives rise to digestive tract 7
2. Ectoderm is the outer layer of cells. It gives rise to the skin and to the nervous system. 3. Mesoderm is the middle layer of cells. It gives rise to the circulatory, skeletal and reproductive systems. C. Symmetry in Animals: Body symmetry refers to the body being cut in two halves having matching shapes. Animals with no symmetry are asymmetrical (sponges). Radial symmetry is based around the point in the central axis of a tube (anemone). Animals like humans have two equal halves, bilateral symmetry. The sides of the body have special names: dorsal, ventral, anterior, posterior, medial, lateral, proximal, and distal. Kinds of symmetry: PAGE 185 Fig 6.17 1. Asymmetrical: lack symmetry, cannot be cut into two matching halves (eg.) most sponges 2. Radial symmetry: division into equal halves by passing a plane through the central axis of the animal in any direction (eg.) starfish, jellyfish. 3. Bilateral symmetry: division into equal halves only along a single plane. Each half is a mirror image of the other (eg.) most animals, humans (not perfect) Spatial relationships (bilateral symmetry): Dorsal - upper side or back Ventral - lower side or belly Anterior - front region or head Posterior - hind, rear, or tail end Lateral - side Note: Animals with bilateral symmetry have a true head. It shows cephalization which refers to a concentration of nerve tissue and receptors at the anterior end of the animal s body. D. Complete/ Incomplete Digestive Tract Incomplete: The body plan has only 1 opening to gut. Food and waste enter and leave through single opening. 8
Complete: Tube within a tube body plan, in which there are two openings to the gut. E. Body cavity: A coelom is a fluid filled cavity surrounded by the mesoderm a layer of epithelial cells that line the body cavity and gut; (found in all vertebrates and many invertebrates). Importance of a body cavity: 1. Provides space where internal organs can be suspended without being affected by muscle pressure and body movement 2. Provide space for internal organs to develop and expand 3. Contain fluids which may assist in internal transport of nutrients, and gas exchange; contains a peritoneum which is a covering membrane that lines the body cavity and covers the internal organs. Less complex vertebrates have a pseudocoelom, a fluid filled cavity of variable shape which has no peritoneum. Animals with a fluid-filled body cavity or coelom are called coelomates. Animals with a fluid-filled cavity and no peritoneum are pseudocoelomates. Animals without a coelom are called acoelomates. The development of a body cavity demonstrates complexity and evolutionary development in animals. The simplest animals have a single opening that acts as a mouth and anus. Complex animals have a gut with two openings, a mouth and anus. ** Table # 3: Invertebrates. Developmental trends Invertebrates: 1. We go from simple to complex as organisms evolve. 2. Simplest organisms have asymmetry. As complexity increases, we go to radial and finally bilateral symmetry. 3. Organisms go from having no cavity to a false cavity to a true body cavity. 4. Simpler organisms may reproduce sexually and asexually. As complexity increases, organisms reproduce only sexually. 5. Simpler ones have two tissue layers, more complex have three tissue layers. 6. Sessile to motile. 7. Simpler ones have no tissue, no systems. As complexity increases, the more systems an organism has (both in # and complexity). 9
Note: Many invertebrates are hermaphrodites (contain male and female parts), but rarely can they self-fertilize. ** Table # 4: Vertebrates. Common characteristics for all vertebrates would be: i) presence of a notochord (backbone) that runs along the dorsal length of the body. The notochord occurs only in the embryo and is then replaced with bone or cartilage. ii) a dorsal nerve cord to allow nerves to branch out to all parts of the body. iii) gill slits in the pharynx or throat. For terrestrial vertebrates, gill slits only occur in the embryo. (In humans, one of the gill slits develops into the ear canal!!) General Characteristics: 1. endoskeleton, appendages, and skin 2. closed circulatory system with an increasingly complex heart structure 3. increased cephalization (concentration of nerve tissue in anterior region) and increased size and complexity of the cerebrum 4. presence of a coelom to hold increasingly complex systems for digestion, excretion, reproduction, circulation and respiration Evolutionary developmental Trends - Vertebrates: 1. Adaptations leading from total dependence on water to survival on land (evolutionary trend from external fertilization towards internal fertilization). 2. Development of a more complex heart structure (from a two chambered to three chambered to four chambered heart). 3. Increase in cephalization 4. Increase in size and complexity of the cerebrum (anterior part of brain). 5. Body system functions increase in complexity with evolution. Why arthropods are the most successful class of animals? The main characteristics of an arthropod are: exoskeleton, jointed appendages, segmented bodies, and an open circulatory system. They are found in a wide range of habitats. It seems that they have evolved from a segmented ancestor. They undergo 10
sexual reproduction with internal fertilization and separate sexes: (although some may be hermaphroditic). Diversity (Phylum Arthropoda) is due to their: 1. rigid, jointed external skeleton or exoskeleton (for protection). This is made of chitin which provide a waterproof protective armour. This is shed periodically as they grow. 2. well-defined head with jointed appendage. These are specialized body segments fused into distinct regions such as head, thorax and abdomen. These are adapted for a wide range of functions such as sensory reception, eating, etc. 4. well-developed nervous system. Arthropods have a larger brain than their nearest relatives. 5. different structures and functions for obtaining nourishment. They eat plant and plant material, animal tissues such as blood, and feed on members from other kingdoms. Example of the Frog Life Cycle (as an example of an animal): (See Figure 6.26, p. 193). A frog is an example of an amphibian. A frog will undergo external fertilization; (the sperm and egg meet outside the bodies of both parents).the male frog produces the sperm and the female frog produces the eggs. Fertilization of frog eggs is external. During mating, the male frog mounts a female frog and helps to squeeze the eggs from the female s body. The male will then release sperm on top of the eggs. Once an egg has been fertilized, development begins immediately. The larva of the frog or tadpole will emerge from the egg in a few days. The young tadpole has a tail for swimming and gills for respiration. This tadpole stage of a frog may last a few months up to two years, depending on the frog species. Tadpoles eat plants and algae. The tadpole will undergo a complete change in form or metamorphosis; (older tadpoles start to develop legs). This metamorphosis usually takes one or two months and the young frog will have welldeveloped legs, but no tail. It eventually becomes an adult frog fully adapted for life on the land. 11
SUPPLIMENTARY HANDOUT KINDGOM ANIMALIA BODY SYMMETRY 12