IB Biology Topic 5: Evolution / Biodiversity

All species are descended from ancestral species

Mechanism that drives changes in species is natural selection

Sharing a common ancestor (jack rabbit and snowshoe hare)

Struggle for existence: tendency of species to overproduce results in direct competition between members of species

Natural variation: differences among members of same species

Role of environment: selects individuals with traits best-suited for environment

Darwin says heritable traits drive evolution, Lamarck says acquired traits drive evolution (traits inherited throughout lifetime rather than genetically)

1. fossil record

2. geographic distribution

3. comparative anatomy

Fossils are chronological; however deep they are in the Earth is a rough estimate of how long they've been there.

Closely related but different: Descendants of single ancestral species pass on adaptations best suited to that habitat

Distantly related but similar: descendants of different species living in similar habitats share similar adaptations

Homologous structures: similar structures in species with common ancestor

Vestigial structures: important to ancestral species but no clear function in modern descendants (wisdom teeth, appendix)

Analogous structures: anatomically different structures with same function (insects, birds, bats all have wings)

-       Changing of allele frequencies within a population

-       Allele and genotype frequencies will remain constant from gen to gen in the absence of other evolutionary influences

o   No environmental differences, no reason to change so stays constant

-       Large population

-       Random mating (no sexual selection)

-       No mutations

-       No migration between populations

-       All genotypes reproduce with equal success to be passed on (no selection)

Reality: Populations don’t follow these rules so microevolution occurs

-       Monohybrid cross (Aa x Aa) create 1:2:1 genotype frequency

o   25% homozygous dominant, 50% heterozygous, 25% homozygous recessive

-       Form of natural selection where certain traits are favoured

-       Human controlled, selects desired traits to breed

-       Drives microevolution quicker while reducing genetic variation

-       Unfavourable traits also passed on with favourable due to multiple alleles on chromosomes

genes exchanged between populations, occurs when individuals migrate

-       Selective pressures within environment affecting frequencies of traits

o   Directional selection: favours one end of phenotypes

o   Diversifying/disruptive selection: favours extreme ends of phenotypes

o   Stabilizing selection: favours middle phenotypes

-       Bottleneck effect: reduces size of gene size immensely due to natural disaster

o   Reduces genetic variation, some alleles present more frequently

-       Founder effect

o   Colonization of habitat impacts gene pool, increases founder genes

Biological change on large scale

• speciation/extinction

Offspring is viable and fertile

-       Formation of new species where members of parent species are unable to continue reproducing due to physical or behavioural barrier

-       Over time, members of the new species will not mate with parent species (behavioural barrier)

-       Change in geology separate different populations (canyons, colonization)

-       Hybrid infertility – offspring viable not fertile (mule)

-       Hybrid inviability – nonviable offspring

-       Mechanical isolation – physical incapable (brodyboena snails have different shell spirals)

-       Behavioural isolation – different courtship (birds)

-       Temporal – different breeding season

-       Habitat isolation - Same geographic location, species live in different habitats (bottom vs top of lake)

Divergent – different species evolve from common ancestor due to habitat differences (snowshoe hair vs jackrabbit)

Convergent – distantly-related species living in similar habitats develop similar adaptations (analogous structures like wings)

Gradualism: small, constant, changes slowly over time

Punctuated: Periods of small change with times of huge change in 1-2 traits, is due to mutations in genes of few individuals

• results in rapid change within next few generations

Kingdom (ex. Fungi, Animals, Plants)

Phylum

Class

Order

Family

Genus

Species

King Phillip Came Over For Great Spaghetti

o   Archaea – extreme high/low conditions

o   Eubacteria – salmonella, e. coli

o   Protista – single celled, aquatic

o   Fungi – yeast, mushrooms

o   Plantae – plants

o   Animals

-       Small, nonliving material that can infect all types of organisms

o   Coat of proteins surrounding genetic information

o   Cannot survive outside of a host

-       Genetic material (DNA/RNA)

-       Protective protein coat - capsid

DNA/RNA (Single stranded + capsid)

Bacteriophage - infects bacteria (can be either)

Some bacteria can have glycoproteins, possess different shapes

1.     Attachment: attaches to host cell

2.     Entry: virus/DNA enters cell

3.     Replication: uses host cell to create parts of virus (genetic material, spike proteins)

4.     Assembly: various components of virus are assembled into virus

5.     Release: host cell bursts (lysis)

cycle takes 25-45 mins, can create 100+ viruses per cycle

Virus naturally reproduces alongside cell, acts as parasite

-       Can be pre-emptively treated with vaccines made from dead/weakened virus particles

o   Results in immune system to make attack cells (lymphocytes) to destroy the specific virus from vaccine

-       mRNA sequence derived from spike protein

o   encapsulated into lipid coating

-       cells begin to produce copies of spike proteins

o   triggers body to produce lymphocytes against protein

-       uses harmless virus (adenovirus) to contain spike proteins

-       can be stored in regular fridge conditions

Viruses are host specific

-       Wide range: rabies can get rodents, dogs, humans

-       Narrow range: human flu only occurs in upper respiratory tract

when virus passed from animal to human (mad cow)

Hypothetical solution for sickle cell anemia

-       Harmful genetic material in virus removed and replaced with functioning human gene, placed into capsid

o   Virus can then infect human cells to insert the correct gene into human DNA

Limitations: virus does not control where DNA is inserted, may cause unwanted mutations

-       Series of yes/no questions about organism characteristics to aid in classification

prokaryote bacteria found in extremely harsh environments (salty, hot, anaerobic)

typical prokaryote bacteria (true bacteria) - salmonella, e.coli

Shapes:

• coccus - spherical

• bacillus - rod shaped

• spirillum - spiral

Grouping

o   Diplo – paired

o   Staphylo – clustered

o   Strepto – long chains

o   Gram positive – lots of peptidoglycan (glycoprotein), thick cell wall

o   Gram negative – less peptidoglycan, thin

o   Asexual – binary fission

o   Sexual – known as conjunction, transfers chromosome to another cell then binary fission

o   Gene transfer – pilus acts as bridge, exchanges plasmid containing DNA

o   Spore formation – allows bacterial to survive in harsh conditions

• Forms spore coat, contains DNA → goes dormant (endospore)

o   Photoautotroph – photosynthesizes

o   Photoheterotrophs – use light to create ATP, consumes organic matter for carbon (NO CO2)

o   Chemoautotrophs, use CO2, no light, use inorganic matter (NH3 / H2S) for energy via chemosynthesis

o   Chemoheterotrophs: consume organic molecules for energy and carbon; most bacteria are chemoheterotrophs, e.g. decomposers and parasites

o   Obligate aerobes – requires oxygen

o   Obligate anaerobe – cannot tolerate oxygen, use anaerobic processes (glycolysis) to obtain ATP

o   Facultative anaerobe – use oxygen when possible, use fermentation when anaerobic conditions

1.     Stain bacteria with crystal violet dye

2.     Treat with alcohol or acetone

3.     Stain again with red or pink dye

a.     Gram positive bacteria: will retain violet dye as peptidoglycan absorbs crystal violet dye well

b.     Gram negative bacteria: violet dye is washed out in Step 2, then absorbs pink dye in step 3, therefore has less peptidoglycan due to less absorption properties

Mostly single celled eukaryotes, not bacteria but bacteria-like

difference between bacteria and protists is prokaryote vs eukaryote

• animal like (protozoa, ciliate, zooflagellate)

• algae like (Euglenophyta, Chrystophyta)

• fungi like (slime mould)

• Single-celled, motile heterotrophs classified by how they move: via cilia, flagella, or pseudopodia (false feet)

• Digest food in vacuoles formed by a process known as phagocytosis (“cell-eating”)

• Entamoeba hystolitica – intestinal parasite in humans causing dehydration, causes amebic dysentery

-       Cytoplasmic extensions of false feet, produce ameboid movement

-       Food vacuoles

-       Contractile vacuole helps with water regulation, contraction movements

-       Phylum Mastigophora

-       Use one or more flagella for movement

-      free-living or parasitic

• Trypanosoma: requires two hosts, uses insect as host (not affected), infects mammal causing Chagas disease and sleeping sickness

-       Phylum ciliophoran

-       Uses multiple cilia covering cell membrane to move, travels along in spiral path rotating along sine wave

o   ex. Paramecium species

-       Micro and macro nucleus

-       Mouth/anal pore, specified pores for digestive functions

-       Perform conjugation (sexual reproduction)

Paramecium join at mouth pore and exchange DNA from micronucleus, then conduct mitosis

• Autotrophic via photosynthesis

• Flagella, motile protists

• Use photosynthesis as main, can become heterotrophic in low light

• Can move towards light source using eyespot

• Have both mitochondria and chloroplast

• Pellicle – flexible film covering cell membrane

o Found in freshwater, sea, land

o Some have a shell made of silicon dioxide

o Food is stored as oils

o Certain diatoms can be indicator species, also useful in fossil dating

• Spend some of their life cycle as single cells, can aggregate to form colonies

• phylum myxomycota

-       Eukaryotic heterotrophs, lack chloroplasts

o   Multinucleate – multiple nuclei

-       Cell walls made of chitin, polymers of glucose derivative, contains nitrogen

-       Except yeast, most are multicellular with long thread-like cells called hyphae, Grow in masses called mycelia (single mycelium)

-       Growth of hyphae only occurs at tip, allows for colonization of organic matter

-       Consumes food via absorption (saprotrophs)

o   Asexual reproduction favourable during harsh conditions and need for quicker population

o   Sexual requires greater investment of energy, more time, creates greater genetic diversity

- Fewer than 1000 species

o Bread molds, parasites of plants and animals - Multinucleate hyphae

- Reproduce asexually using spores produced by structure called sporangia

• Sexually reproduced by forming zygospore, fusing mating hyphae together

-       30k species

o   Yeast, multicellular fungi

-       Asexual reproduction by budding, sexual by forming ascus (sac), fuse

-       Commercial importance for baking, brewing (ferments alcohol), gene research

o   Uses yeast

-       Decomposers and parasites

-       Can cause diseases

• Ophiostoma ulmi causes Dutch Elm tree disease

• Claviceps purpurea causes wild ergot, affects crops, natural source of LSD

-       Mushrooms

o   The cap/stem is called fruiting body where spores are produced

-       Body has short lifetime, vegetative mycelium lives in soil, survives for years

-       Some produce poisons/hallucinogens

o   Amanita phalloides is death cap mushroom

-       Incapable of sexual reproduction

o   Blue-green mold

-       Classified by asexual spore

-       Trichophyton causes ringworm and athlete’s foot

-       Fungi that live symbiotically with other organisms

-       Lichens – symbiosis between fungus and photosynthetic algae or bacterium

-       Mycorrhizae – zygomycete or basidiomycete that lives in symbiosis with roots of plants

o   Plants receive nutrients from fungus, fungus receives carbs from plants

-       Eukaryotic autotrophs via photosynthesis with cellulose cell walls

-       Many hermaphroditic (produce both gametes)

• mosses, liverwort

-       Non-vascular (no veins, leaves, stems, roots)

-       Small, grow close to ground in moist areas, high SA/V ratio

-       Sensitive to air pollution

-       Life cycle includes alternation of generations (alternate between gametophyte production [haploid] and sporophyte generation [diploid, do not reproduce])

-       Peat mosses genus Sphagnum becomes acidic when release hydrogen ions into environment, inhibits growth of other organisms

o   Very absorbent, holds 20x its dry mass in water

-       Vascular (have veins to transport water, nutrients, gases through plants)

-       Larger due to transport system (leaves, stems, roots)

-       Reproduction involves alternation of generations (seedless vs seed-bearing)

• ferns

• belong to Phylum Tracheophyte

-       Stems grown in soil, vessels called xylem (water) and phloem (food) for transport

-       Have true roots with conducting tissues

-       Asexual reproduction by spores produced in sporangia

• woody plants, belong to Phylum Tracheophyte

-       Non-flowering seed plants – gymnosperms

• gymnosperms are any vascular plant that reproduces by means of an exposed seed, or ovule

-       Cone-bearing and/or evergreen

o   Yew is not cone-bearing, larch is not evergreen

-       Most are soft wood, yellow pine is hard wood

-       Leaves may be needle-like (pine) or scale-like (Cedar)

• main flora of the earth

• flowering plants; have concealed seeds within mature ovaries

• can be classified into 2 evolution lines: monocots, dicots

Monocots

-       One-seed leaf (cotyledon – amount of seed leaves)

-       Parallel leaf venation (ex corn)

-       Scattered vascular bundles

-       Fibrous root system

-       Floral parts (petals) in multiples of 3

o   Trillium flower

Dicots

-       Two-seed leaves (2 cotyledons)

-       Vascular bundles arranged in rings

-       Taproot system (carrot)

-       Floral parts (petals) in multiples of 4

o   daisy

General structure:

• Petals - attract pollinators

• Sepals - protect developing bud

• Receptacle - connects flower to stem

• Stem - connects vascular system to roots

Reproductive organs:

Stamen (male):

• anther - produces pollen

• filament - supports anther, allows for extension so wind/pollinators can spread pollen

Carpel/Pistil (female)

• stigma - receives pollen

• style - pollen tube development

• ovary - produces eggs inside ovule

• aquatic sponges

• multicellular

-       no organs or body systems

-       cellular digestion (heterotrophic)

o   eats small plankton

o   obtain food by filter feeding (catches food via current)

-       asymmetrical bodies

-       Sessile – do not move

-       Skeleton composed of spongin (soft) and spicules (hard)

o   Sexual – sperm and eggs

o   Asexual – regeneration

• Prone to breakage, can regenerate to a certain degree

-       Amoebocytes – specialized cells within sponge responsible for intake of nutrients and waste management

-       Choanocytes – collar cells

o   Layer of cells with flagella, keeps water current going through sponge

o Food vacuoles digest plankton and other organisms

• jellyfish, hydra, sea anemone, coral

-       Have cnidocytes - stinging cells found on tentacles

o   Jellyfish have no stinging on their cups (head), only tentacles

-       Physiology

o   Tentacles

o   Cnidocytes

o   Nematocysts (prickly barbs)

o   Gastrovascular cavity (digestion), abdominal with vessel like network

-       Most have radial symmetry

-       Body forms

o   Polyp (vase shaped)

o   Medusa (cup shaped)

-       Big jellyfish with tentacles, Portuguese man of war

-       Hydra – freshwater cnidarian, polyp

o   Participates in asexual reproduction, cloning

-       Coral reefs are skeletons of cnidaria

Flatworms

1. 3 germ layers

   o   Endoderm, mesoderm, ectoderm

2. Bilayer symmetry

3. Cephalization – has a head

-       Acoelomates – have no fluid filled body cavity

-       Ingestion

o   Free-living – carnivores or scavenger, have digestive cavity (mouth pharynx)

o   Parasites – feed on blood/tissue of a host, no digestive system, absorbs nutrients directly from host

-       Reproduction

o   Sexual – hermaphroditic

o   Asexual – fission, split in two and regenerate

-       Some are harmless – planaria

-       Cause disease

o   Tapeworms from uncooked meats

Flukes from unsanitary water – schistosamo mansoni

-       Thin bodies allow for diffusion for exchange of nutrients

-       Flame cells - remove excess water

-       Ganglia – nerve cells control functions in place of a brain

-       Eyespot – group of cells detect light

-       Movement

o   Cilia glide through water

o   Muscle like cells help them twist/turn

Roundworms

1. Unsegmented worms

2. Pseudocoelom – fake coelom

3. body cavity containing organs

-       Free-living or parasitic

-       Reproduce separately, not hermaphroditic

-       Diseases

o   Trichinosis in muscles from uncooked food (trichinella)

o   Filaria causes elephantiasis

o   Ascaris from feces infects eyes, bowel

o   Soil hookworms burrow into skin

Segmented worms (annelida)

• Classes: Earthworms (Oligochaeta), marine worms (polychaeta), leeches (hirudinea)

-       With coelom

-       “Little rings,” body segments separated by septa (internal walls)

-       Septa have bristles called setae

-       Closed circulatory system and advanced nervous system

-       mostly sexual reproduction, some hermaphroditic

o   some ability to regenerate

Earthworms

-       streamlined bodies with few setae

-       live in soil or freshwater

-       castings – worm feces enrich soil

Marine worms

-       sandworms, lood worms

-       paired paddlelike appendages with setae (looks like centipede feet)

Leeches

-       external parasites with suckers

-       medicinal uses for breaking blood clots

o   no longer used

• clams, snails, slugs, squid, octopi, and others

• Mollusca = “soft”

Soft bodied with internal/external shell

Body plan:

o   Foot: takes on many forms

o   Mantle: covers the body

o   Shell: present in most

o   Visceral mass: internal organs

• Gastropods (no shell or single shelled)

  • Move by a muscular foot

  • Some are poisonous with bright colours

  • ex. snails, slugs, limpets and nudibranchs (sea slug)

• Bivalves → things with two shells

  • ex. Clams, scallops, mussels

• Cephalopods → Soft-bodied with head is attached to a foot which is divided into tentacles with sucking disks

  • ex. octopi, squids, cuttlefish, nautilus

  • Have small internal shells or no shell at all

    • Nautilus – only shelled cephalopod

  • Squid have a modified shell called a pen

  • Have well developed eyes; most complex of all molluscs

Starfish, brittle stars, sand dollars, sea urchins, & sea cucumbers

-       Marine, unsegmented coelomates; “spiny-skinned” animals

-       Endoskeleton known as a test is made of calcium plates called ossicles w/spines

-       Metamorphosis: bilateral, free-swimming larva → sessile or sedentary adult

-       Adults have pentaradial (5 part) symmetry with 5 arms

-       Breathe through skin gills; no circulatory, respiratory, or excretory systems

-       Arms capable of regeneration; asexual reproduction

Physiology

-       Ventral (lower) surface = oral surface where mouth is located

-       Dorsal (upper) surface = aboral surface where anus is located

Spiders, insects, crustaceans

-       Jointed appendages on a segmented body

-       Exoskeleton: skeleton on outside

-       Mandibles: chewing mouthparts

-       Metamorphosis: egg → larva → adult

3 subphylum: Chelicerata (spiders, scorpions, ticks), crustacea (shrimp, lobster, crab), Uniramia (centipede, millipede, bees)

spiders, ticks and scorpions

• 2 body segments: cephalothorax (head & chest), abdomen

• 8 legs; no antenna

shrimp, lobsters, crabs, crayfish

• 4 pairs of legs; 2 claws called chelipeds

• 2 pairs of antennae

-       Centipedes

o   Predators, poisonous

o   1 pair of legs per segment

-       Millipedes

o   Herbivores

o   2 pairs of legs per segment

-       Other insects (bees)

o   3 pairs of legs

o   1 pair of antennae

o   3 body segments (head, thorax, abdomen)

Mostly vertebrates; mammals, birds, fish, reptiles, amphibians

-       General characteristics

o   Notochord: firm, flexible rod of tissue located on the dorsal side of the body which is a part of the endoskeleton (spine in humans)

o   Dorsal nerve cord: hollow tube to the notochord connected to brain (spinal chord)

• Pharyngeal pouches: small pouches of the anterior digestive tract

  • Gills in aquatic chordates

  • Jaws connected to inner ear, tonsils in terrestrial

o   Post-anal tail: consists of muscle tissue behind the posterior opening of the digestive tract, tail extends beyond anus

All chordates will have all aspects at some point during lifetime

Non-vertebrate chordates (sea squires, tunicates)

• bodies covered by a tough covering, or tunic

• shoot out a stream of water when touched

  • sessile, barrel-shaped, sea bottom filter feeders

  • Adults DO NOT have a notochord, dorsal nerve cord, or post-anal tail

• Skeletons consist of bone and/or cartilage

• Brain is protected by a cranium

• Well developed 2-4 chambered heart with a closed circulatory system

-       All sexual reproduction

-       Spawning – fish lay eggs, fertilized externally

o   Some fish can do live birth

-       Oviparous: lays eggs

• chickens, frogs

-       Ovoviviparous: eggs stay in mom

• sharks, rays, snakes

-       Viviparous: babies get nourishment from mom.

• Ex. Humans, cats, some fish

• must have gills, fins, scales

• Devionian Period - Age of Fish

• 2 chambered heart - blood is oxygenated from gills

  • some fish have lungs - lungfish

Physiology

• fins help with movement

• gills

  • operculum - gill covers

• swim bladder - maintains buoyancy

mechanism in fish that maintains water balance

• salt water loses water

• freshwater gains water

  • salmon can do both

o   Cerebrum – thinking, voluntary activities

o   Cerebellum - coordination and balance

o   Medulla oblongata – functions of internal organs

o   Lateral line system – sensing vibration

frogs, axolotl

-       “double life” → lives in water then land

-       Moist skin

-       Metamorphosis from fish

• Bones become stronger

• Have lungs to breathe air

• Walk on land

-       Feeding

o   Larva are herbivores with gills

o   Adult frogs – carnivores with lungs

o   Some have gills for whole life – mudpuppy

-       Respiration

o   Double loop, 3 chambers, partially divides ventricle

-       Reproduction

o   Lay eggs, fertilization external - spawning

Orders: Crocodilia (crocodile, alligator), Testudines (turtles and tortoises), Sphenodonta (tuatara), Squamata (lizards, snakes) → largest group

-       Strong, bony skeletons with clawed feet

-       Ectothermic – cold-blooded

-       Dry, scaly skin

-       Oviparous - lay amniote eggs

-       Respiration with lungs

-       3 chambered, Ventricle divided heart (crocodilia have 4)

-       Amnion: watery environment

-       Yolk: food for embryo

-       Allantois: stores waste

-       Chorion: membrane, gas exchange

-       Albumen: egg white, cushion

-       Forelimbs modified into wings

-       Feathers

-       Hollow, lightweight bones

-       Endothermic (warm-blooded)

-       Efficient respiration

-       Heart with a completely divided ventricle (4 chambers)

-       Scaly feet (birds are related to reptiles)

-       Furculum (wishbone)

o   Down feathers – provide insulation

o   Contour feathers – cover head and body, provide colouration

o   Flight feathers – on wings/tail, provide lift

o   All feathers covered in oil to waterproof, secreted from preen gland

→ Preening can repair broken links on the vanes

-       Aerodynamic feathers

-       Efficient digestive, respiratory, circulatory systems

-       Strong chest muscles

-       Lightweight bones

-       Beak/feet shape related to food

o   Hooked beaks tear meat

o   Long sharp beaks for spearing fish