Plants, Fungus, and Animals

Coevolution

• Coevolution is when two species are so closely connected that their adaptations benefit each other.
  • Example: Hummingbirds and flowers. Hummingbirds have long bills adapted to reach nectar in flowers and also collect pollen during this process.
  • The adaptations lead to a dependency between the species.
  • Common in plants and their pollinators, showcasing many coadaptive traits.

The Dodo Bird and the Dodo Tree

• The dodo bird, endemic to Mauritius, is a classic example of coevolution.
  • It coevolved with a tree known as the dodo tree, which produced large fruits with thick-coated seeds.
  • When the dodo ate the fruit, it helped rub off the seed coat in its digestive system, improving seed viability.
• Extinction of the dodo bird occurred due to:
  • Human introduction of dogs for hunting.
  • Habitat changes by humans.
  • Resulting in the dodo bird's rapid extinction and subsequent failure of the dodo tree to sprout its seeds.
• Scientists attempted to use similar-sized birds (like chickens) to help the dodo tree's seeds germinate but with little success.

Plant Hormones

• There are five major plant hormones essential for growth and reproductive processes:
  • Auxins
  • Stimulates stem growth, influencing overall growth in stems and roots.
  • Used in experiments to encourage new cell growth when applied to damaged plant parts.
  • Ethylene
  • Vital for fruit ripening; emitted as a gas.
  • Causes other fruits to ripen when in proximity, hence special storage for bananas in supermarkets.
  • Cytokinins
  • Aid in cell differentiation and growth.
  • Abscisic Acid
  • Slows growth and induces dormancy during unfavorable conditions (e.g., winter).
  • Important for plants in temperate ecosystems, helping them withstand seasonal changes.

Plant Responses to Stimuli

• Plants exhibit movement and growth adjustments towards stimuli.
  • Phototropism: Growth towards light.
  • Gravitropism: Roots grow downwards, and stems grow upwards, regardless of seed orientation in soil.
  • Thigmotropism: Response to touch or irritants, for example, petals may close during heavy rain to protect against damage.

Flowering in Plants

• Plants can be classified based on light conditions influencing their flowering cycles:
  • Short Day Plants: Require more darkness to flower (e.g., Christmas cactus, Poinsettias).
  • Long Day Plants: Prefer extended daylight to flower, commonly flowering in spring and summer.
  • Experiments show the necessity of uninterrupted dark periods for triggering flowering in short-day plants.

Communication Among Plants

• Research indicates plants can communicate danger and share resources through volatile organic compounds (VOCs).
  • Plants can emit green leafy volatiles in response to damage, which informs nearby plants of danger.
• Lead research visualized this communication by modifying plants to show calcium ion activation in real time.

The Insect Impact on Plants

• Insects are responsible for about 20% of plant damage on Earth due to diseases and predation.
• Strategies plants might employ against insect predators include:
  • Mast Years: Producing a large abundance of seeds (e.g., oak trees dropping many acorns at once).
  • Dual purpose of high seed production is to ensure some survive predation.
  • Pathogens: Biological agents causing diseases in plants, classified as biotrophic (sustaining the host) and necrotrophic (killing the host).

Fungi Overview

• Fungi are their own kingdom, distinct from plants and animals.
  • More closely related to animals than plants due to shared characteristics.
  • Primarily saprobes, extracting nutrients from decaying material.
  • Characterized by absorption rather than ingestion of food.
• Key Structure of Fungi:
  • Hyphae: Filamentous structures forming the main body of fungi.
  • Mycelium: Collection of hyphae, often hidden underground.
  • Spores: Reproductive units essential for fungal propagation, particularly seen in mushrooms.
• Yeast is an exception, being unicellular and reproducing through budding.

Introduction to Animals

• Animals are multicellular eukaryotic organisms that are primarily heterotrophic.
• The animal kingdom evolved about 580 million years ago.
• Two main characteristics of animals include:
  1. Ingestion of nutrients, contrasting with fungi's absorption.
  2. Compartmentalization: specialized cells forming tissues and organs.

Animal Evolution and Characteristics

• Animals exhibit various levels of complexity depending on their evolutionary history.
  • Invertebrates (~95% of animals): Lack a backbone, such as sponges, insects, and mollusks.
  • Vertebrates (~5% of animals): Have backbones, including mammals, birds, reptiles, amphibians, and fish.
• Invertebrate Classes: Sponges (oldest), jellyfish, and more complex structures evolve over time.
• Phylogenetic branches illustrate the evolutionary relationships among different animal species.
• Coelom Classification:
  • Acoelomate: No body cavity (e.g., flatworms).
  • Pseudocoelomate: Partial body cavity (e.g., nematodes).
  • Coelomate: Complete body cavity (e.g., all vertebrates).

Animal Adaptations and Habitats

• Animals exist in diverse ecosystems: freshwater, saltwater, and terrestrial.
• Saltwater habitats are most stable, providing a consistent environment for survival, followed by freshwater.
• Terrestrial habitats pose many challenges like drying out, leading to specific adaptations for moisture retention.
• Symmetry Types in Animals:
  • Asymmetrical: No symmetry (e.g., sponges).
  • Radial Symmetry: Equal parts around a central axis (e.g., sea stars).
  • Bilateral Symmetry: Divisible into mirror-image halves (common in most vertebrates).

Conclusion

• Overview of plants, fungi, and animals highlights mutual dependencies, evolutionary adaptations, and ecological roles within ecosystems.
• Understanding these kingdom-wide dynamics lays foundational knowledge for studying ecology and evolution in further classes.