1

BIOLOGY - 2201 .Unit 2 : BIODIVERSITY.

Characteristics of Living Things:

Living things — are organized systems made up of one or more cells.— metabolize matter and energy.— interact with their environment and are homeostatic.— grow and develop.— reproduce themselves (biogenesis).— are adapted to their surroundings.

If something does not have these characteristics (cells, biogenesis growth and development,metabolism, water requirements, organic compound production, reproduction with inheritance andadaptations), then it is not considered a living thing. A fox would be a living thing whereas a rock wouldnot (ie.) nonliving.

Classification: How to classify living organisms on the earth?

Classification refers to organization (ie.) to place ideas or groups together on the basis of similarity.Taxonomy is the branch of biology that deals the classification of living things. A person who works inthis field is a taxonomist. A classification system is a way to identify an organism and place it into thecorrect group with related organisms. It is also a way of referring to an organism by name so that scientists in each part of the world can understand each other regardless of language (ie.) a universalsystem.

The first attempt at classification was made by the Greek philosopher, Aristotle, over two thousandyears ago. There were about 1000 different organisms identified at this time. Aristotle used a two-kingdom system for classifying organisms — Kingdom Animalia and Kingdom Plantae. In hisclassification scheme, animals were classified by where they lived (land, water, air) and plants accordingto structure (herbs, shrubs, trees). Why was this not a good system ? (eg.) Bats and mosquitoes areair dwellers. Ants and mice are land dwellers. Which organisms are more closely related ?

A student of Aristotle , Theophrastus , grouped plants according to reproductive structures and types ofexternal tissues. Invention of the microscope and the discovery of microorganisms forced scientists torethink the criteria for classification. The microscope was instrumental in the discovery ofmicroorganisms. For example: Euglena — Is it an animal or plant? It is a photosynthetic plant thatmoves like an animal. This set the stage to have a third kingdom. I n 1866, Ernst Haeckel, a Germanbiologist, proposed a third kingdom called Protista to classify micro-organisms (which were neitherplants nor animals).

As biologists learned more about structure and the way of life of different organisms , they added morekingdoms to the classification system. Fungi were once included in the plant kingdom. Fungi are notphotosynthetic and are heterotrophic (obtain food from other sources). They become a separatekingdom called Fungi.

2

In1969, Robert Whittaker, a biologist at Cornell University, proposed a 5 Kingdom classificationsystem based on: a) number of cells; b) presence or absence of a nucleus; c) mode of nutrition. Thissystem gained wide acceptance, but it has been replaced by a six-kingdom system currently used bymany biologists.

Our text uses a 6 - kingdom classification system.Kingdoms : 1. Animalia

2. Plantae3. Fungi4. Protista5. Bacteria6. Archaea

The three domains of life :1) Domain Bacteria – Kingdom Bacteria2) Domain Archaea – Kingdom Archaea3) Domain Eukarya –Kingdoms Protista , Fungi, Plantae, Animalia

Although bacteria and Archaea are prokaryotic , RNA evidence shows that they are as different fromeach other as either is from eukaryotes. That is why biologists have created a new level of classificationabove kingdoms, the domain.

Six Kingdom System :

Plantae : multicellular ; specialized tissues and organs ; photosynthetic autotrophs ; most are non- motile.

Animalia : multicellular ; specialized tissues and organs ; heterotrophs ; most are motile at somepoint in life cycle

Fungi : unicellular or multicellular ; heterotrophs ; absorb nutrients ; nonmotile

Protista : unicellular , colonial , or multicellular ; autotrophs or heterotrophs ; some are motile

Bacteria : majority are unicellular; some are colonial or link up in chains to form filaments ; autotrophs or heterotrophs ; microscopic ; no membrane - bound organelles (ie.)prokaryotic; movement by flagella or no movement at all; 3 main shapes — cocci(round), bacilli (rod-shaped), and spirilli (spiral-shaped)

Archaea : survive in extreme environmental conditions such a hot springs, volcanoes, etc. ;biochemically and genetically different from bacteria; 3 main shapes — cocci (round),bacilli (rod-shaped), and spirilli (spiral-shaped);

Note : Eukaryote has a membrane bound nucleus while a prokaryote has a cell with no membranebound nucleus.

3

Modern taxonomy : Modern taxonomy is based on the work of Carolus Linnaeus, a Swedishbotanist (1707 - 1778). He is said to be the founder of modern taxonomy. He based his system on thestructural similarities in organisms. Each group in this system is referred to as a taxon (pl., taxa). Thetaxa are arranged from the largest and broadest division, a Kingdom, to the smallest and most specific,a species. People could accurately identify an organism by comparing its characteristics against achecklist.

Hierarchical classification of a Human:1) Kingdom Animalia2) Phylum Chordata3) Class Mammalia4) Order Primates5) Family Hominidae6) Genus Homo7) Species sapiens

Linnaeus used a two word naming system. It was based on Latin or Greek. New species are givenLatin names. They are usually descriptive or may honour a scientist or historical figure.To distinguishbetween degrees of similarity each Kingdom is divided into progressively smaller groups. Each group iscalled a taxon — (Kingdom , Phylum , Class , Order , Family , Genus , Species). These range fromgeneral to specific. The species taxon includes members that resemble each other so closely that theycan interbreed and produce fertile offspring.

Nomenclature refers to a system for naming living things. The two-word naming system for eachspecies is called binomial nomenclature. The name of the genus is the first word and is capitalized.The species is the second word. The entire system is based on starting with the general and moving tothe specific. Each kind of organism has a two-word Latin name called its scientific name.

(eg.) Felis domesticus / Felis leo / Felis tigris

Sometimes the genus can be abbreviated. For example, the fruit fly is Drosophila melanogaster andcan be abbreviated to D. melanogaster.

Many new organisms and some sub - groups have been added. Most large plants and animals havecommon names, which can lead to confusion. Modern techniques consider the evolutionary history of aspecies (called phylogeny). A phylogenetic tree is used to show the relationships among variousorganisms. (See Figure 4-14, p. 116) The phylogenetic tree represents a hypothesis about theevolutionary relationships among a group of phylogeny). A phylogenetic tree is used to show therelationships among various organisms.

Cladistics: Cladistics refers to a classification scheme that is based on phylogeny. It is based on theidea that each group of related species had one common ancestor, and organisms retain some ancestralcharacteristics and gain some unique derived characteristics as they evolve and diverge from thecommon ancestor. ( p.117)

4

Why not use common names to identify different species? - Many different common names for same animals.- Many different tree species called mahogany.- Common names can give misleading information.

Modern techniques used to help classify organisms — How organisms are classified:

1. Evidence from fossil records : Radioactive dating is the use the decay of carbon-14 to findthe ages of some organisms. They can then tell if they were ancestors of some species. Proteincomparisons of amino acid sequences are checked for similarities and differences. The bloodproteins in horseshoe crab reveal that it is more closely related to spiders than crabs.

2. Evidence from anatomy : Structural information is the comparison of bones found incertain animals. For example, the human arm , horse’s leg , bat’s wing , whale flipper are allquite similar. They have similar arrangement and the similarities of bone structure indicate thesame evolutionary origin.

3. Evidence from embryonic development : Comparative embryology is the comparisons ofearly embryonic development. For example, tunicates, in their larval stage, have structures thatare similar to tadpoles such as long dorsal nerve cords and a flexible notocord. They aretherefore classified with other vertebrates.

4. Evidence from biochemistry — (DNA): Biochemical techniques can look at the arrangement of amino acids. For example, human blood and baboon blood are very closetherefore humans are more closely related to baboons than horses. Similar DNA patternswould suggest that the relationship between organisms is closer.

5. Evidence from DNA : DNA analysis is a good way measuring the closeness of relationshipsamong organisms.

6. Metabolic Behaviour such as the ability to digest certain substances or if an organism is aproducer, a consumer, or a decomposer can also be used in classifying organisms.

In Summary :

Area of Science Type of Evidence

anatomy homologous structuressimilar appearance

biochemistry similarity in amino acid sequence of importantproteins

DNA similarity in DNA nucleotide sequence

phylogeny classification based on common ancestry

5

Dichotomous keys : A dichotomous key is an identification key that uses a series of pairedcomparisons to sort organisms into smaller and smaller groups.

- used as a way to classify organisms-available for almost all living things-used by all types of scientists- consists of many numbered steps- first few steps key on gross external features- moves from general to specific- each step contains two or more statements of which only one is true about a single organism- the true step directs the user to the next step or to the organism

A key is a listing of specific characteristics, divided into two equal parts. A dichotomous key is aseries of two choices or opposing statements, known as a couplet. Some specific characteristics foridentification of organisms could be structure and function.

A Point to Consider : No classification system is etched in stone. The advantage of the Linnaeussystem is its adaptability. This is evident in the fact that today biologists use a six-kingdom classificationsystem as compared to a five-kingdom classification system.

General Characteristics of the Six-Kingdoms :

Kingdom

Characteristic Archaea Bacteria Protista Fungi Plantae Animalia

cell type prokaryotic prokaryotic eukaryotic eukaryotic eukaryotic eukaryotic

nutrition heterotrophs(absorption)

photo-synthesis;chemo-synthesis;absorption

photo-synthesis;ingestion orabsorption

absorption photo-synthesis

ingestion

body form mostlyunicellular;some colonial

mostlyunicellular;some colonial

mostunicellular;some simplemulticellular

mostmulticellular

multicellular multicellular;organs andorgan systems

reproduction asexual asexual asexual andsexual

asexual andsexual

sexual sexual

locomotion present insome

present insome

present insome

absent absent present

NOTE : A More- Detailed Reference : See Table 1 : Kingdom Worksheet (a handout).

Core STSE #1 : “Modern Classification Techniques”

6

A VIRUS :Viruses are not organisms. They do not have any cellular structure and are not classified into any of thesix kingdoms of classification. Viruses are very successful at invading the cells of organisms becausethey can only reproduce using the metabolism of a host cell. Viruses consist of strands of DNA or RNAsurrounded by a protective protein coat called a capsid. Virus particles have a variety of shapes;(determined by the type and arrangement of proteins in the capsid).

A virus cannot replicate (reproduce) without a host. It is believed that viruses probably originated asfragments of nucleic acid that escaped from their original cell. They survived becoming parasitic onspecific hosts. This would suggest that viruses and their hosts probably evolved together. This wouldmake a virus and a host more closely related than a particular virus with other viruses.

Example of Viral Reproduction : T4 virus — Lytic Cycle (steps in viral replication): (See Figure 4.21, p. 123).

1) Attachment: The T4 phage is a complex virus that attaches to a specific receptor site on ahost’s (such as E. coli) cell wall. Weak chemical bonds form between the attachment andreceptor sites, adhering the virus to the host.

2) Entry (Penetration): T4 injects its nucleic acid (DNA) into the host (E. coli). The viral DNApasses through the core and into the cell. The capsid remains outside.

3) Replication: Host protein synthesis is stopped by viral degradation of host DNA. The host’smetabolism will replicate the viral DNA (or RNA).

4) Assembly: Spontaneous assembly of new virus particles occurs.

5) Lysis and Release: The host cell, (ie.) E. coli’s plasma membrane and cell wall, lyses (orbreaks open), releasing the new virus particles. The host (E. coli) cell dies.

Kingdom Bacteria : Bacteria are simple, prokaryotic organisms. They can be classified according to shape : cocci (round-shaped); bacilli (rod-shaped) and spirilli (spiral-shaped). Bacterial cells reproduce by means ofasexual reproduction (one parental cell gives rise to 2 or more identical offspring). It is the process ofbinary fission in bacterial cells.(p. 134 - 135)

Example of Life Cycle of Eubacteria and Archaebacteria : The bacterial cell, (E. coli), reproduces by binary fission. (See Figure 5.4, p. 134).

1. As the bacterial cell grows, it makes a copy of its original, single chromosome.2. The cell elongates and separates into the two chromosomes.3. Cell partition or septum forms between the two chromosomes.4. The septum completes itself and distinct walls form.5. The cells separate and two new cells are produced.

7

Kingdom Protista : Protists are microscopic, eukaryotic organisms. They are classified into three major groups accordingto their type of nutrition. The groups are:

1) Protozoa (animal-like protists) : heterotrophs that ingest or absorb food.2) Algae (plant-like protists) : autotrophs that carry out photosynthesis.3) Slime moulds and Water moulds (fungus-like) : heterotrophic.

Example of a Protist Life Cycle: (See Figure 5.15, p. 146).Plasmodium vivax (a human parasite), a Sporozoan (Phylum Sporozoa), is responsible for one type ofmalaria in humans.

1. A mosquito bites an infected person and ingests the reproductive cells of the Plasmodiumpresent in red blood cells.

2. The gametes (reproductive cells) fuse to form a (diploid) zygote inside the gut wall of the mosquito and divide many times to form numerous spore-like fragments or sporozoites. Thezygote breaks open releasing the sporozoites (spore cells).

3. The sporozoites migrate and invade the salivary glands of the mosquito. From here, they will beinjected into a new human host when bitten by the mosquito.

4. Once inside the new human host, sporozoites will reproduce asexually in the liver to form asecond type of sporelike cell. The cells leave the liver and enter the bloodstream where theyinvade red blood cells. Once inside the red blood cells, they multiply at a very rapid rate.

5. Red blood cells rupture releasing toxic substances and spores. These spores infect other redblood cells. The cycle repeats itself when a mosquito bites the infected person.

8

Kingdom Fungi : Fungi are non-photosynthetic heterotrophs that grow in the ground and possess cell walls. They havesome plant-like qualities. The bodies of fungi are made up of a network of fine filaments called hyphae(singular hypha). A loose, branching network of hyphae that makes up the bulk of a fungus is called amycelium. Fungi are classified according to their reproductive characteristics. They are : 1) Zygomycotes — zygospores — sexual reproduction.

2) Basidiomycotes — basidiospores — sexual reproduction.3) Ascomycotes — asci (spores spread by wind) — sexual reproduction.4) Deuteromycotes — conida — asexual reproduction.

Example of a Fungus Life Cycle : (See Figure5.28, p. 154).Rhizopus stolonifera is the common black bread mould. The small black dots or fuzz on bread are thereproductive structures of the bread mould. The bread mould reproduces by asexual reproduction, butcan also reproduce by sexual reproduction when times are unfavourable (producing zygospores). Theseare diploid cells that contain two copies of every chromosome. Rhizopus belongs to the PhylumZygomycota or the zygospore fungi.

Sexual Reproduction Phase: The zygospores develop after two haploid (monoploid) hyphae ofopposite types (+ and - mating strains) combine and fuse together to form the zygospores. The breadmould is made up of two forms of hyphae. The horizontal hyphae are the stolons and the downwardgrowing hyphae are the rhizoids . The stolons spread out over the surface of the bread while therhizoids anchor the mycelium to the bread surface. The rhizoids secrete enzymes that digest the food(the bread) and then absorb the digested nutrients. A thick wall develops around the zygospore forprotection. The zygospore will remain dormant until conditions are favourable for growth. Once thishappens, the zygospore will absorb water and the nuclei will undergo meiosis.

Asexual Reproduction Phase: The bread mould will develop sporangiophores, a third form of hyphae.The sporangia or spore-bearing capsules are located at the ends of the sporangiophores. Theasexual sores develop inside the sporangia and are released when the capsules split open.

Kingdom Plantae (Plants) :

Botany is the study of plants. All plants are said to have a common ancestor; (ie.) it is thought thatplants have evolved from an ancient group of green algae. Plants and green algae share a commonevolutionary ancestry.

The general characteristics of plants are the following :I) photosynthesisII) ability to absorb water and nutrientsIII) ability to conserve water and reduce the drying effect of airIV) process of gas exchangeV) presence of supporting tissuesVI) ability to reproduce

12

Table # 2 : Plants

Kingdom Animalia (Animals) :

Zoology is the study of animals. Animals are multicellular and eukaryotic. Animals consume organicmaterials and digest it and are termed heterotrophs . Most animals are motile at some time in theirlives through some simple forms are attached to a substrate (sessile). Many animals have tissuesspecialized for specific functions (nerve tissue, muscle). Many lower forms have simple asexual andsexual reproduction while higher forms reproduce sexually exclusively.There are two main types of animals, vertebrates and invertebrates. A vertebrate has a backbonewhile an invertebrate has no backbone (no bones at all usually!!!)

Chracteristics of Various Animal Phyla :- body organization (cells organized into tissues, organs and organ systems)- number of germ layers (tissues from which more specialized tissues develop)- body symmetry- a complete or incomplete digestive tract- development (or not) of an internal cavity called a coelom

Symmetry in Animals :Body symmetry refers to the body being cut in two halves having matching shapes. Animals with nosymmetry are asymmetrical (sponges). Radial symmetry is based around the point in the central axisof a tube (anemone). Animals like humans have two equal halves, bilateral symmetry. The sides ofthe body have special names: dorsal, ventral, anterior, posterior, medial, lateral, proximal, distal.

Kinds of symmetry :1. Asymmetrical : lack symmetry, cannot be cut into two matching halves (eg.) most sponges2. Radial symmetry : division into equal halves by passing a plane through the central axis of the

animal in any direction (eg.) starfish, jellyfish3. 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 backVentral - lower side or bellyAnterior - front region or headPosterior - hind , rear , or tail endLateral - side

Note : Animals with bilateral symmetry have a true head. It shows cephalization which refers to aconcentration of nerve tissue and receptors at the anterior end of the animal’s body.Body cavity : A coelom is afluid filled cavity surrounded by the mesoderm — a layer of epithelial cells that line thebody cavity and gut ; (found in all vertebrates and many invertebrates).

13

Importance of a body cavity :1. Provides space where internal organs can be suspended without being affected by muscle

pressure and body movement2. Provide space for internal organs to develop and expand3. 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 theinternal organs. Less complex vertebrates have a pseudocoelom, a fluid filled cavity of variableshape which has no peritoneum.

Animals with a fluid-filled body cavity or coelom are called coelomates. Animals with a fluid-filledcavity 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 gutwith two openings, a mouth and anus.

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 tract2. 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.

r See the completed table below for a summary of invertebrate characteristics:

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).

Note : Many invertebrates are hermaphrodites (contain male and female parts) , but rarely can theyself-fertilize.

14

r See the completed table below for a summary of vertebrate characteristics:

Table # 4 : Vertebrates.

Common characteristics for all vertebrates would be:i) presence of a notochord (backbone)ii) a dorsal nerve cordiii) gill slits

General Characteristics :1. endoskeleton , appendages ,and skin2. closed circulatory system with an increasingly complex heart structure 3. increased cephalization and increased size and complexity of the cerebrum4. 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 (concentration of nerve tissue in anterior region).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, andan open circulatory system. They are found in a wide range of habitats. It seems that they have evolvedfrom a segmented ancestor. They undergo sexual reproduction with internal fertilization and separatesexes: (although some may be hermaphroditic).

Diversity (Phylum Arthropoda) is due to their: 1. rigid, jointed external skeleton or exoskeleton (for protection).

2. well-defined head with jointed appendages3. specialized body segments fused into distinct regions such as head, thorax and

abdomen.4. well-developed nervous system.5. different structures and functions for obtaining nourishment

15

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 eggmeet outside the bodies of both parents).The male frog produces the sperm and the female frogproduces the eggs. Fertilization of frog eggs is external. During mating, the male frog mounts a femalefrog and helps to squeeze the eggs from the female’s body. The male will then release sperm on top ofthe eggs. Once an egg has been fertilized, development begins immediately. The larva of the frog ortadpole will emerge from the egg in a few days. The young tadpole has a tail for swimming and gills forrespiration. This tadpole stage of a frog may last a few months up to two years, depending on the frogspecies. Tadpoles eat plants and algae. The tadpole will undergo a complete change in form ormetamorphosis; (older tadpoles start to develop legs). This metamorphosis usually takes one or twomonths and the young frog will have well-developed legs, but no tail. It eventually becomes an adultfrog fully adapted for life on the land.