Eukaryotes – Kingdom Protista and Kingdom Fungi

Major Characteristics of Eukaryotic Cells

• Eukaryotic cells are defined by the presence of a nucleus and membrane-bound organelles.
• These cells are generally larger and more complex than prokaryotic cells.

Kingdoms in Domain Eukarya

• The four kingdoms belonging to the Domain Eukarya are:
  • Kingdom Protista
  • Kingdom Fungi
  • Kingdom Plantae
  • Kingdom Animalia

Endosymbiotic Theory

• The endosymbiotic theory explains the origin of eukaryotic cells by suggesting that these cells evolved from symbiotic relationships between early prokaryotic cells.
• Some organelles, like mitochondria and chloroplasts, were once independent prokaryotic organisms that were engulfed by ancestral eukaryotic cells.

Kingdom Protista

• Protists are considered to be the first eukaryotic organisms.
• They exhibit a diverse range of forms and functions, from unicellular to multicellular.

Basic Characteristics of Kingdom Protista

• Protists can be autotrophic or heterotrophic, can exist as unicellular or multicellular organisms, and reproduce asexually or sexually.

Nickname of Kingdom Protista

• Kingdom Protista is often nicknamed the "junk drawer" of the eukaryotic world.
• This nickname reflects the high level of diversity and the fact that protists do not fit neatly into the other kingdoms.

Classification of Protists

• Scientists classify protists into three groups based on their method of nutrition:
  • Animal-like protists (protozoa)
  • Plant-like protists (algae)
  • Fungus-like protists (slime molds, water molds)

Animal-Like Protists

• Another name for animal-like protists is protozoa.
• The term comes from Greek, where "proto" means first and "zoon" means animal.
• They are classified as animal-like due to their ability to move and ingest food.

Movement of Animal-Like Protists

• Amoebas move using pseudopods (temporary projections of cytoplasm).
• Paramecium move using cilia (tiny hair-like structures covering their surface).

Plant-Like Protists

• Plant-like protists are collectively known as algae.
• They are considered plant-like because they perform photosynthesis, containing chlorophyll and other pigments.

Algal Blooms

• Algal blooms occur when algae grow excessively in water, often due to high nutrient levels (eutrophication).
• These blooms can produce toxins and deplete oxygen in the water, threatening aquatic life.

Fungus-Like Protists

• Fungus-like protists absorb nutrients from their environment similar to fungi.
• They differ from true fungi in that they can move during some life stages and often have a different cell structure and reproduction methods.
• Examples include slime molds and water molds.

Kingdom Fungi

• Members of Kingdom Fungi have cell walls made up of chitin.

Defining Features of Fungi

• Hyphae are filamentous structures that form the body of the fungus, and they facilitate nutrient absorption.
• Mycelium is a network of hyphae that function as the main body of the fungus.
• A filamentous body allows for extensive surface area for nutrient uptake.

Fruiting Body

• The fruiting body is the reproductive structure of fungi, typically what we recognize as a mushroom.

Energy Acquisition in Fungi

• Fungi obtain energy by digesting organic material externally and then absorbing the nutrients (Digest → Ingest).
• They are classified as heterotrophs, with examples including:
  • Saprophytes (decomposers)
  • Parasites (feed on living hosts)
  • Mutualistic fungi (interacting beneficially with hosts)

Reproduction in Fungi

• Fungi can reproduce asexually through methods such as budding, fragmentation, and spore production.
• Spores are critical for sexual reproduction in fungi and help in dispersal and survival in harsh conditions.

Fungal Symbiotic Relationships

• Lichens are a mutualistic relationship between fungi and algae/cyanobacteria, where fungi provide structure and protection while algae/cyanobacteria provide photosynthesis products.
• Mycorrhizae are fungi that associate with plant roots, enhancing nutrient uptake for plants while receiving carbohydrates in return.

Benefits and Harms of Fungi

• Benefits include:
  • Decomposition of organic material, creating fertile soil.
  • Production of antibiotics and food products.
• Harmful fungi can cause:
  • Plant diseases and crop failures.
  • Human illnesses, such as athlete's foot and ringworm.