SBI3U1 Unit 1: Diversity of Life

Biodiversity

Variety of life on Earth

Biological species concept

Defines species as organisms that can successfully interbreed and produce offspring

Morphological species concept

Classification based on physical traits and characteristics

Phylogenic species concept

Defines species based on evolutionary history and common ancestry

Genetic diversity definition

Variety of genes between organisms of the same species

Species diversity

Number of each and variety of different species within an ecosystem

Autotroph

Organisms that are able to produce their own food

Heterotroph

Rely on other organisms for their food source

Ecological diversity

Variation in the complexity of biological communities

Taxonomy

The science of naming, describing, and classifying organisms based on shared characteristics.

7 taxa

Kingdom, phylum, class, order, family, genus, species

6 kingdoms

Bacteria, Archaea, Protista, Animalia, Fungi, Plantae

3 domains

Bacteria, archaea, and eukarya

Phylogenetics

Study of evolutionary relatedness between species using genetic information

Clade

A branch of a cladogram that represents all the species that share a common ancestor.

Cell theory

Provides a framework for defining the concept of life

Principles of cell theory

The cell is the simplest unit that can carry out all life processes, all cells come from other cells and not non-living matter, all living things are made up of one or more cells

7 characteristics of life

Nutrition, respiration, movement, excretion, growth, reproduction, sensitivity

Virus reproduction

Can only reproduce within host cells

Components of viruses

Genetic material, a capsid, an outer envelope containing surface proteins

Capsid

Protective protein coat

Types of virus shapes

Helical, polyhedral, spherical, complex

Bacteriophages

Viruses that invade and destroy bacteria cells

Vaccines

Contain a weakened or dead form of the virus, or RNA. White blood cells will remember the virus and react quickly when infected

Protists definition

Eukaryotic, not plants/animals/fungi

Evidence for endosymbiosis

Mitochondria and chloroplasts have double membranes like cells, a separate set of DNA similar to aerobic and cyanobacteria, they reproduce independently through binary fission within eukaryotic cells

Human uses of protists

Medical uses, food source, food stabilizers, potential biofuel

Reproduction in unicellular protists

Reproduce asexually and parasexually (binary fission and conjugation)

Reproduction in muticellullar protists

Reproduce sexually by producing spores that fuse to make new offspring

Fungi kingdom features

Chitin cell wall, heterotrophic, immotile, external digestion

External digestion

Hyphae secrete enzymes into the food source that break down nutrients that they then absorb

Fungi phylogeny

Ascomycota, basidiomycota, glomeromycota, zygomycota

Mycellium

A root-like structure through which fungi absorb water and nutrients

Hyphae

Branches of mycelium which are long tubes of cell usually separated by septa that allow sharing of cytoplasm

Fungal spores

Single cells released from mature fungi for reproduction, landing in nutrient rich locations

Fruiting body

Above ground, produces spores which disperse for reproduction, it’s composed of hyphae

Mycorrhizae

Symbiotic relationship where a fungus surrounds the roots of a plant to aid nutrient and water absorption while the plant provides food

Yeasts

Anaerobic unicellular fungi used in food and fermentation.

Lichens

Fungus surrounding other species in its mycelium to protect it and supply water and nutrients, in return supplying the fungus with food.

Fragmentation in fungi (asexual)

A piece of mycelium breaks off the fungus and is able to form a separate (genetically identical) individual

Budding (asexual)

The cell begins growing a clone that remains attached to its membrane, once it reaches maturity it separates into a separate genetically identical organism

Haploid cells

Sex cells with only one copy of an organism’s genetic material

Diploid cells

Cells which have two copies of genetic material

Spores (sexual reproduction)

The fruiting body releases many haploid spores that are dispersed

Sporangia

Structures within the fruiting body that produce haploid spores

Sexual life of a fungus

Spores germinate into haploid mycelium, then fuse to form one cell with 2 haploid nuclei, then fuse into a diploid mycelium, produce a fruiting body and new spores

Tissues

Groups of specialized cells with a shared structure and function working together

Radial symmetry

At embryonic stage, organisms are symmetrical around a central axis

Bilateral symmetry

At embryonic stage, organisms are symmetrical around a left/right axis with distinct heads

Diploblast

Have 2 layers, ectoderm and endoderm, with non-living jelly-like mesoglea between them to provide support

Triploblast

3 layers, ectoderm, mesoderm, endoderm

Ectoderm

Outermost layer, forms skin and nervous system

Endoderm

Innermost layer, forms lining of the gut, respiratory system

Mesoderm

Forms muscle tissue, circulatory system, reproductive and excretory organs

Coelem

Body cavity present in most triptoblasts which allow space for internal organs to expand and contract

Peritoneum

Covers and protects internal organs in the abdomin and acts as a conduit for nerves and blood vessels

Protostomes

At embryonic development, mouth forms before the anus

Deuterostomes

At embryonic development, anus forms before the mouth

Notochord

Elastic rod-like structure in an embryo which directs spinal development

Animal reproduction

Sexual reproduction (egg and sperm produces a zygote), fragmentation, budding, or parthenogenesis

Parthenogenesis

Occurs when a female produces a genetically identical zygote without fertilization by fusing an ovum and a polar body

Plant kingdom traits

Eukaryotic, cell wall made of cellulose, autotrophic, multicellular

Plants share a common ancestor with

A type of green algae called charophytes which both contain chlorophyll and perform photosynthesis

Evolutionary groupings (phyla) of plants

Bryophytes, lycophytes & pteridophytes, gymnosperm, angiosperm

Bryophytes

Seedless nonvascular

Lycophytes and pteridophytes

Seedless vascular

Gymnosperm

Cone-bearing seed vascular

Angiosperm

Flowering seed vascular

Helical virus examples

Tobacco mosaic virus, ebola

Polyhedral virus examples

Adenoviruses (pink eye, common cold, viral pneumonia)

Spherical viruses examples

Coronavirus, influenza

Complex viruses examples

Bacteriophages

Most abundant biological agent on Earth

Bacteriophages

Theories on the origin of viruses

Parasitic living organism that lost its ability to reproduce outside another organism, produced from DNA fragments of a living organism, existed before the first cells

Examples of lytic viruses

Common cold, ebola, COVID-19

Lytic cycle

The viruses hijacks the cells molecular machinery and reproduces itself, eventually the host cell is destroyed and the viruses are released

Lysogenic cycle

Virus incorporates its DNA into host cell’s genome and remains in a dormant state while the host cell divides, when triggered the virus enters the lytic cycle

Viral transmission

Bites, bodily fluid exchange, airborne, physical contact, fomites

Fomites

Objects with viruses on them

Attenuated vaccines

Contains a weakened virus which can replicate without causing disease that triggers an immune response so cells will remember it and quickly respond to the real virus

Epidemic

Large-scale regional outbreak

Pandemic

Global outbreak

Smart particle

A hollowed out virus which is used to deliver therapies directly to diseased areas and leave healthy tissue alone. Molecular tags are attached which act as addresses

Cons of traditional taxonomy

Ambiguous/subjective, following a dichotomous key takes time, morphological features can lead to incorrect classification, different genes can lead to similar structures, evolutionary relatedness is a guess using physical features

Why is modern taxonomy important

Research applies to similar organisms, tracing disease transmission, improving crop yield/disease resistance by crossing species

Prokaryote features

Single-celled, lack nuclei and membrane-bound organelles

Eukaryote features

Nuclei, membrane bound organelles

Bacteria examples

Bacillus anthracis, streptobacilli, staphylococcus

Common bacteria structures

Pilli, ribosomes, nucleoids, flagellum, cell wall, plasma membrane, capsule, plasmid, cytoplasm

Pilli

Hair-like appendages bacteria use to attach to surfaces/other cells

Ribosomes

Perform protein synthesis

Nucleoid

Densely packed loop of bacterium’s DNA

Flagellum

Used for motility

Bacterial cell wall

Rigid peptidoglycan layer that provides support/structure

Plasma membrane

Lipid layer that controls what goes in/out of the cell

Capsule

Thick, slimy protective outer layer

Plasmid

Loop of DNA containing several genes

Cytoplasm

Fluid that suspends cell contents

Prefix diplo-

In pairs

Prefix strepto-

In chains