Variety of Living Organisms (1b)

Unit 1, The Nature and Variety of Living Organisms, b

Bacteria

• Prokaryotes

• Microscopic

• Unicellular

• Cell wall: Peptidoglycan

• Cell membrane

• Cytoplasm

• Plasmids

• No nucleus: circular chromosome of DNA

• Some photosynthesise (no chloroplasts but have chlorophyll-like substances and sugar-digesting enzymes), but most are heterotrophs, some are saprotrophs

• Eg: Lactobacillus bulgaricus, Pneumococcus

Viruses

• Not considered alive

• Don't carry out 8 life processes

• Only reproduce inside a host's metabolic pathways

• Smaller than bacteria

• Parasitic

• Infect every type of living organism

• No cellular structure: protein coat and only one type of nucleic acid (RNA or DNA)

• Ex: TMV, HIV, Influenza

TMV

Tobacco Mosaic Virus

• First virus to be isolated by scientists

• Infects about 150 species of plants, including tomatoes and cucumbers

Symptoms

• Causes a distinctive pattern of discolouration since it affects chloroplasts

• Plant won't grow- lack of photosynthesis- reduces yield

Spread

• Spread by direct contact

• Stays in soil for 50 years

Cure

• No treatment

• Method of control: good hygiene

• Farmers use TMV-resistant crop variants

Main Eukaryote Kingdoms

• Plants

• Animals

• Fungi

• Protoctists

Plants

• eukaryotes

• multicellular

• cellulose cell walls

• chloroplasts: can photosynthesise

• store carbohydrates as starch or sucrose

• ex: flowering plants, legumes, cereals

• no nervous coordination

Animals

• eukaryotes

• multicellular

• no chloroplasts: no photosynthesis

• no cell walls

• nervous coordination and locomotion

• store carbohydrates as glycogen

• ex: mammals and insects

Fungi

• eukaryotes

• mostly multicellular but some unicellular

• made of mycelium consisting of hyphae

• chitinous cell walls

• feed by secreting enzymes onto decaying organic matter, then absorb the digested molecules → Saprotrophism

• some are parasitic and feed on living material

• store carbohydrates as glycogen

• ex: Mucor, Yeast, Athlete’s Foot, Ringworm

Protoctists

• different from other 3 types of eukaryotes

• unicellular and multicellular, but sometimes aggregate to form colonies

• some are more like animals → Amoeba

• some are more like plants (cell walls and chloroplasts) → Chlorella

• pathogen → Plasmodium

• some are autotrophs, others are heterotrophs

Influenza

3 different Influenza viruses infect humans to cause the flu

• A, B, C infect the cells that line airways

• cause high temperature, body aches, fatigue

• A causes most cases of the flu globally

HIV

HIV can lead to AIDS

Symptoms

• starts with flu-like illness

• can stay hidden for many years until the immune system can no longer deal with other infections or cancers → late stage HIV (AIDS)

Spread

• direct sexual contact

• exchange of bodily fluids, like blood, when needles are shared

• from mother to child during birth or in breast milk

Cure

• no cure

• antiretroviral drugs used early can effectively slow/halt the progress to AIDS