Biology 20. Characteristics of Life

Transcription

1 UNIT 3 BIODIVERSITY Chapter 4 Diversity of Life Biology 20 Characteristics of Life Generally speaking we all know what is living and what is non-living A butterfly is alive, while a rock is not A tree is living, while a building is nonliving Rather than defining what life is, biologists tend to describe what makes something living What are the characteristics that are shared by all living things? 1

2 Thinking Lab In pairs, examine the pictures on pages Brainstorm a list of characteristics that enable you to separate living from non-living Make a list of 6 more living and non-living things (3 of each) and trade with another group to test the reliability of you characteristics Modify your list as needed 6 Characteristics of Living Things Organized systems made up of one or more cells Cells make up tissues, tissues make up organs, organs make up systems. Non-living things do not have this level of complexity Metabolize matter and energy Chemical reactions require a source of energy food 2

3 6 Characteristics of Living Things Interact with their environment and are homeostatic stay the same in an environment even though they are exchanging molecules / water from their surroundings Grow and Develop Unicellular living things grow, and divide. Multicellular living things grow, develop through the union of eggs and sperm, followed by cell divisions 6 Characteristics of Living Things Reproduce themselves Only living things can make other living things like themselves. Genetic information being passed on to offspring Adapt to their surroundings Have physics feature that make them well suited to the environment in which they live behaviours for obtaining food, waste transport, motility, reproduction and communications 3

4 Road to 6 Kingdom Classification We often tend to organize things based on physical characteristics Music, clothing, books The groupings reflect the patterns we see in the world around us Aristotle first grouped over 1000 organisms into 2 large kingdoms, then subdivided each into smaller groups 1. Kingdom Animalia Grouped based on movement: on land in the air in water 2. Kingdom Plantae Grouped based on physical characteristics Reproductive structures Types of external tissues Road to 6 Kingdoms 3. Kingdom Protista Discovery of microorganisms forced scientists to reconsider Aristotle s system of classification Some organisms move like animals, but photosynthesize like plants 4

5 Road to 6 Kingdoms 4. Kingdom Fungi Were originally included in the plant kingdom Were placed in their own kingdom because they do not photosynthesize, and absorb nutrients from their environment Road to 6 Kingdoms 5. Kingdom Bacteria Entirely made up of prokaryotic cells (lacking a nucleus and membranebound organelles) Obtain energy from a wide range of environments, but thrive between 10 and 40 degrees celcius Also called: Monera, eubacteria (true bacteria) 6. Kingdom Archaea Also made up of prokaryotic cells, but with specialized structures allowing them to live in extreme environments Hot vents, acidic lakes, high pressure, low oxygen, etc. Also called: archaebacteria 5

6 The Three Domains Each of the kingdoms belongs to one of the three domains They represent how organisms evolved See fig. 4.5 pg Domain Bacteria Kingdom Bacteria Earliest living organisms, 1000 s of species exist today 2. Domain Archaea Kingdom archaea Evolved later, through a series of changes in bacteria 3. Domain Eukarya Kingdoms protista, plantae, animalia and fungi Early protists branched away from bacteria, giving rise to all the other kingdoms Living Things Domain Bacteria Domain Eukarya Domain Archaea Kingdom Bacteria Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia Kingdom Archaea 6

7 Naming and Classifying Organisms There are well over 2 million different types of organisms known. Biologists place the organisms into groups based on their characteristics. By classifying, biologists can organize living things into groups. Taxonomy The branch of Biology that deals with the naming and placing of all organisms into groups. The system of naming we use today was created over 300 years ago by Carolus Linneaus The Linnean system is very simple to use and became popular as a result Naming Organisms Many of the names are based on the Latin or Greek since that is what was used when the naming system was created. Scientists are required to give new latin scientific names when they discover new species The names often reflect the characteristics of the organisms, or in some cases honour the discovering scientist 7

8 Hierarchy of Groups Each kingdom is subdivided into smaller and smaller groups called taxa (one taxon) Kingdoms are the largest taxa, containing 1000 s of species Species are the smallest taxa, containing only one type of organism The Taxa Domain Kingdom Phylum (plural Phyla) Order Family Genus (plura genera) Species Each taxon may have subtaxa Hierarchical Classification The Pneumonic Domain Kingdom Phylum Order Family Genus Species Doctor King Phyllip Ordered the Family Genius to Speak Each organism is classified based on physical characteristics and DNA relationships The Species level contains organisms that are similar enough that they can reproduce 8

9 Domestic Dog Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Canidae Genus Canis Species familaris Different breeds may exist Humans Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species Sapien Sapien 9

10 Binomial Nomenclature Binomial = 2 terms Nomenclature = naming System of naming species using a two-term name First term is the genus name Second term is species name Rules for naming The genus name is capitalized The second name is the species and is entirely lower-case The name must be either in italics or have each term separately underlined Binomial Nomenclature Examples CORRECT WAY Canis familiaris house dog OR Canis lupus Wolf Many species may be in the same genus because they are related, in this case dog-like animals WRONG WAY Canis Familiaris canis lupus Canis latrans - Coyote Canis lupus 10

11 Common Names In addition to scientific names organisms may also be given common names. Common names can cause confusion Why do you suppose this is? Example Pg 112 A. Shellfish B. Starfish C. Jellyfish D. Crayfish E. Catfish Why are these names misleading? Benefit of Universal Naming A universal system of naming allows us to avoid the confusion associated with common names, and tells us something about evolutionary relationships. 11

12 Dichotomous Keys A tool used by biologists to identify unknown organisms Consists of a series of paired comparisons of characteristics used to sort organism into smaller and smaller groups Today s Classification Schemes Taxonomists (scientists who name organisms) use a variety of information to classify or group organisms The goal of taxonomy is to determine the evolutionary history of organisms This is done by comparing physical characteristics of modern species with past species Scientists utilize many techniques to ensure that organisms are classified correctly Using these techniques many species have been re-classified after being incorrectly so in the past 12

13 Evidence: Fossil Record Using radioactive carbon- 14 dating, the age of a fossil can be determined C-14 decays at a known rate, the amount remaining in a fossil can be used to calculate the age This evidence shows that major taxa are not as different from each other as they appear Archaeopteryx shares features with both birds and reptiles. The organism is believed by many to be a modern descendant of birds That is to say the intermediate between dinosaurs and birds Evidence: Anatomy Comparisons are made between the structures of different organisms Bone structures are similar in many species, even though their sizes and proportions have been modified for different modes of transportation See Fig. 4.9 pg

14 Evidence: Biochemical Many genes are simply instructions for making proteins By comparing these genes and finding similarities means that different species may be related since they have the same proteins Many species have been reclassified based on their biochemistry Guinea pigs Horseshoe crabs Evidence: Embryology Comparisons of early embryological development between different species provides evidence as to how closely related they are Earnest Haeckel drew embryos of different species for comparison 14

15 Haekel s Embryo Drawings Evidence: DNA / RNA Analysis Mixing single strands of DNA from two different species to determine percentage of relationship The greater the bonding between complimentary base pairs, the more closely the two are related This is done using DNA from the mitochondria because it is passed down from mother to offspring (from the egg) 98% of human chimp DNA bonds while only 93% of human-macaque monkey DNA bonds To which species are we more closely related? 15

16 Phylogeny & Cladistics Phylogeny The whole evolutionary history of a species or other taxonomic group. (Figure 4.14 pg. 116). At the base of the tree is the oldest ancestor Forks in branches represent divergences of new species The top of the tree represents the most recent time, so from the base to the top of a branch is a progression through time. Cladistics A classification scheme based on phylogeny and the idea that any one group of related organisms was derived from a common ancestor Phylogenetic Trees Cladogram A diagram similar to a phylogenetic tree that does not take into account the time of a divergence. 16

17 Phylogenetic Tree of Life Viruses Non-living particles of DNA/ RNA encased in a protein capsid. The capsid helps to protect the virus from the host cell s defensive enzymes, and enables the virus to be more host-specific Capsid 17

18 Why Viruses are non-living 1. No cell structures 2. No cytoplasm, organelles or cell membranes 3. No cellular respiration Lytic Cycle (Viral Replication) A. ATTACHMENT The virus particle must first attach itself to a host cell, generally to a specific receptor site on the cell membrane. B. ENTRY 2 ways this can happen: Injection of the DNA/RNA into the host cell (T4 virus) OR if the virus in an envelop, it will attach to the cell membrane, and the cell will engulf it, forming a vacuole, which it will break out of releasing DNA/RNA C. REPLICATION (lytic cycle cycle of viral replication) The host cell s metabolism replicates (copies) the viral DNA/ RNA D. ASSEMBLY - New virus particles are assembled inside the host cell E. LYSIS AND RELEASE - The host cell breaks (lyses) open releasing the new virus particles 18

19 Lytic Cycle Diagram See page 123, figure 4.21 in textbook Lysogenic Cycle Lysogenic cycle Genetic material from the capsid is released into the host cell. The viral DNA becomes part of the host cell s chromosome as a provirus. The provirus remains inactive but is replicated with the host cell DNA. The newly replicated viral DNA may then be used in the assembly of new virus particles, continuing on in the lytic cycle. EXAMPLE: Cold Sores caused by the herpes simplex virus. The sores appear when the virus is destroying cells, and disappear when the virus is in the provirus stage. Virus may remain dormant in the provirus phase for years meaning viral outbreaks may be very rare even though the person carries the virus. 19

20 Retroviruses Retroviruses Viruses, such as the AIDS, human immunodeficiency virus (HIV) Are able to transcribe a single strand of RNA into double-stranded DNA using an enzyme called reverse transcriptase This DNA is incorporated into host genome, and replicated each time the host cell divides This forms new virus particles, which repeat the process HIV AIDS Virus Particle Process described in Fig. 4.22, page 124 disease/animations.html MORE ON VIRUSES T4 viruses may be used by genetic engineers to copy genes that they are using for their research. (Fig. 4.23, page 125) DNA/ RNA may be either single stranded or double stranded, and either linear or circular. 70% of all viruses are known to be RNA virus, and since RNA replication frequently involves errors, there is a high rate of mutation in RNA viruses 20

21 Animal Behavior We will study two types of animal behavior. You are the mouse in the maze. The first type is instinctive behavior. Instinctive behavior is something the animal is born knowing how to do. Examples include fish swimming and geese migrating. What other examples can you think of? 21

22 The other type is learned behavior. As you can probably guess, learned behavior is not instinctive. Animals are not born knowing what to do or how to do it. Learned behavior is learned by experience and sometimes from a parent. Examples include lions and leopards learning how to hunt by watching and practicing with their mothers. Your behavior think, think, think What parts of your behavior are instinctive? What parts are learned? Who do you learn from? Name three things you have learned in the last week. 22

23 Kingdom Animalia A Brief Survey of Animals The study of animals is referred to as zoology. Animals are the largest of the 6 kingdoms, and exhibit a great diversity in form and function. 23

24 Major Animal Characteristics 1. Multicellular, eukaryotic organisms, with a division of labour amongst cells that are specialized. 2. A variety of systems have evolved and are specialized for specific functions. These systems include: - Circulatory - Lymphatic - Integumentary (skin) - Digestive - Respiratory - Muscular - Endocrine - Nervous - Excretory - Reproductive - Skeletal 24

25 3. Heterotrophic: Animals have more complex systems than plants. These systems are based upon the animal s nutrient requirements. 4. Locomotion: Most are mobile at some point in their lifetime. 5. Reproduction: This may be through sexual or asexual means. Asexual occurs in some lower forms, sexual occurs in all higher forms. 25

26 Five Major Areas Used to Describe Animals 1. Systems: When moving from simpler to more complex animal forms, the number and complexity of systems increases. 2. Symmetry: This is a term used to describe the body plan of an animal. To find the symmetry of an animal, an imaginary line is drawn to divide the animal in half. There are three forms of symmetry: (A) Asymmetric - An organism cannot be cut into two matching halves. (e.g. sponges) (B) Radial - Any line passing through the central axis of an organism divides it in half. These organisms are rounded. (e.g jellyfish) (C) Bilateral: An elongated body plan. There is only one line that divides the animal in half. This line runs down the middle of the longitudinal section. This is the most common form of symmetry. (e.g. humans, frogs, etc.) 26

27 3. Coelom A coelom is a body cavity. The presence or absence of a fluid-filled cavity is one of the most significant features of animal body plans used in classification. The coelom is located between the digestive tract and the body wall. Importance of a Coelom (i) They provide space in which internal organs can be suspended so they are not negatively affected by muscle pressure and body movement. (ii) They provide space for internal organs to develop and expand. (iii) They contain fluids which may assist in internal transportation and nutrient and gas exchange. Lower animal forms have no or partial coeloms (also called a pseudocoelom). They are at a disadvantage in light of the efficient functioning of a true coelom. 27

28 4. Cell Layers: Animals contain either two or three embryonic cell layers. Simpler animals contain only two; all others have three. Each layer is responsible for producing various tissues and structures in the adult animal. These layers include: Ectoderm - forms the outer body (skin, nerves) Mesoderm - forms the middle organs (kidney, heart) Endoderm - form lining of gut or digestive tract simple animals have no mesoderm. 5. Reproduction: Moving from simpler to more complex animal forms, the reproductive system becomes more complex. 28

29 Classification There are two major groups of animals. They are classified according to the presence or absence of a backbone. Invertebrates 1. These organisms lack a backbone, and include the following phyla: (a) Porifera (sponge) (b) Coelenterata (jellyfish) (c) Platyhelminthes (tapeworm) (d) Nematoda (ringworm) (e) Annelida (earthworm) (f) Mollusca (shellfish) (g) Arthropoda (insects) (h) Echinodermata (starfish) 29

30 2. Make up 97% of the animal kingdom. 3. Higher forms are characterized by cephalization. This is an evolutionary tendency towards specialization of the body with concentration of sensory and neural organs in the anterior end. 4. They possess body plans which have been enormously successful both ecologically and evolutionarily. Kingdom Plantae A Brief Survey of Plants 30

31 The study of plants is called botany. Plants are believed to have evolved from green algae. The main plant (land) characteristics are as follows: 1. Common cellular structures: - all are eukaryotes - multicellular - cell wall composed of cellulose - chlorophyll contained in chloroplasts - produce starch as carbohydrate food reserve - central vacuole 2. Photosynthetic organisms: autotrophs / producers 3. Most are stationary. 4. Reproduction occurs through a life cycle called alternation of generations. The cycle consists of two generations: (a) Sporophyte generation - reproduces asexually (b) Gametophyte generation - reproduces sexually 31

32 The advantage of alternation of generations is the combined advantage of sexual and asexual reproduction. Asexual - only one parent needed Sexual - produces much genetic variety Classification of Plants There are two major groups of plants. They are classified according to the presence or absence of vascular tissue. Vascular tissue is a special tissue for support and for the transport of materials within the plant. There are two forms of vascular tissue: Xylem: This transports water and minerals up the stem of the plant into the leaves. Phloem: This transports glucose produced by the leaves, during photosynthesis, down the stem and into the roots. 32

33 The two groups that plants are divided into: 1. Bryophytes: These include mosses, liverworts, and hornworts. These plants do not possess vascular tissue. They are short plants that usually grow in areas that have a good supply of water. The gametophyte generation is dominant. 2. Tracheophytes: These include horsetails, ferns, gymnosperms, and flowering plants. They have well-developed vascular tissue. The sporophyte generation is dominant. 33

34 Bryophyte (moss) 34

35 Tracheophyte (fern) Tracheophyte - Gymnosperm (fir tree) 35

36 Tracheophyte - Angiosperm (fruit-bearing and flowering) Bryophytes (Moss plants) (i) Lack vascular tissue. This accounts for the remaining characteristics. (ii) Lack true roots, stems, or leaves. (iii) Small in size, growing close to the ground (1-5 cm) (iv) Restricted to moist environments. (v) Transitional group between aquatic and terrestrial plants. (vi) Major forms include moss, liverwort, and hornwort. 36

37 Bryophyte Adaptations for Life on Land 1. Water Conservation - waxy waterproof covering called a cuticle or cutin found on leaflets 2. Gas Exchange - pores found on the top of the leaflets 3. Internal Transport - occurs by diffusion, no vascular tissue 4. Internal Support none 5. Water Absorption - small filaments called rhizoids 6. Reproduction - dependent upon water to move sperm to the egg 37

38 Moss Life Cycle Tracheophytes (i) Possess vascular tissue (xylem and phloem). This accounts for the remaining characteristics (ii) Possess true roots, stems, and leaves. (iii) Large in size, growing well above the ground. (iv) Not restricted to moist environments; well distributed over the Earth s surface. Can even exist in areas where water is scarce. (v) Most complex group of plants. (vi) Major forms include: (a) ferns (b) gymnosperms - produce seeds in cones, 750 species dominant in cold regions and higher altitudes (c) angiosperms - produce seeds in flowers, species. Most dominant plant because: 38

39 Types of Tracheophytes Reasons for Angiosperm Success: (A) animals and insects help pollinate them: (i) presence of brightly colored flowers attracts insects. That is the purpose of the coloration. (ii) presence of nectar to attract insects that aid in pollination. (B) seed coat (fruit) protects and nourishes the embryo (C) seed dispersal also aided by wind (D) fruit covering the seed aids in dispersal. Animals will eat the fruit and drop the seeds, or the seeds will pass through their digestive systems. 39

40 Flower & Seed Structure There are two forms of angiosperms: A cotyledon is a seed leaf and is important in seed germination. It is a modified leaf of a seed plant embryo and can help provide nourishment for the developing embryo. It is one of the first leaves to appear during germination. A monocot has one cotyledon and a dicot has two. Examples: Monocots - grasses, corn, tulips, and palms. Dicots roses, maples, oaks, peanuts, potatoes, etc. Most angiosperms are dicots. 40

41 Trachoephyte Adaptations for Life on Land 1. Water Conservation - cuticle or cutin present on leaves. 2. Gas Exchange - pores called stomata found on the bottom of leaves. 3. Internal Transport - contains vascular tissue 4. Internal Support - vascular tissue 5. Water Absorption - system of roots is present 6. Reproduction - water is not required for movement of sperm to egg except in the case of ferns. In gymnosperms and angiosperms, sperm is contained inside a pollen grain that is moved by wind and insects. Gas Exchange Stomata are better for gas exchange for the following reasons: (1) No holes in the waterproof covering. (2) In the shaded area of the leaf (less water loss). (3) They won t become clogged by dust and other materials. 41