Herbivory and Trophic Levels

Herbivory

• Trophic levels describe an organism's position in a food chain, based on its feeding relationships.
• Primary producers (1st trophic level): Autotrophs (plants/algae) converting solar energy into chemical energy via photosynthesis.
• Gross primary production (GPP): Total energy produced through photosynthesis.
• Net primary production (NPP): GPP minus energy used for respiration. NPP is the energy available for herbivores.
• Primary consumers (2nd trophic level): Herbivores that feed on primary producers.
• Secondary consumers (3rd trophic level): Carnivores consuming herbivores.
• Tertiary consumers (4th trophic level): Predators consuming secondary consumers.
• Energy flows through the ecosystem from primary producers to higher trophic levels.
• Approximately 10% of energy is transferred to the next trophic level, with the rest lost as heat.
• Herbivory is a crucial part of regulating plant populations impacting energy flow in ecosystems.

Food Chains and Food Webs

• Primary producers (plants/algae) at the base of the food chain capture energy from the sun.
• Primary consumers (herbivores) eat producers, passing energy to higher trophic levels.
• Consumers at higher levels eat consumers below them in the food chain.
• Food webs are more complex than food chains. They show all interconnected feeding relationships within a community.

Energy Flow

• Energy from the sun is the primary source of energy in most ecosystems
• Energy flows through ecosystems, becoming less available at higher trophic levels (the 10% rule).
• Energy transformations within trophic levels are largely inefficient.

Detritivores, Carnivores, Herbivores, Omnivores, Scavengers, Decomposers

• Detritivores: Consume detritus (dead organic matter) (e.g., earthworms).
• Carnivores: Consume other animals (meat) (e.g., lions).
• Herbivores: Consume plants (e.g., cows).
• Omnivores: Consume both plants and animals (e.g., humans).
• Scavengers: Consume dead animals (e.g., vultures).
• Decomposers: Break down dead organic matter into simpler compounds to release nutrients (e.g., bacteria and fungi).

Plant Defenses

• Plants use various mechanisms to deter herbivores, including physical defenses (thorns, spines) and chemical defenses (toxins, irritants).

Sclerophylly and Divaricate

• Sclerophylly: Describes tough, rigid leaves, often found in dry environments, to conserve water and deter herbivores.
• Divaricate: Describes a plant growth form with branches spreading widely apart, to reduce herbivory and deal with wind/light.

Biodiversity

• Biodiversity is the variety of life on Earth.
• Biodiversity includes microorganisms, plants, animals.
• Current estimates range from 1.5-2 million identified species with 8.7 million estimated total species.
• Phylogenetics studies how organisms evolved from common ancestors using morphological/genetic traits.
• Biodiversity is essential for ecosystems and human well-being (food, shelter, health, climate).

Binomial Nomenclature

• A naming system for species using two Latin words, the genus and species.
• Species names are italicised.
• The genus name is capitalized, the species name is not.

Phylogenetic Trees

• Show evolutionary relationships among species.
• The root of a tree represents the last common ancestor of all species in the tree.
• Branches represent evolutionary lineages.
• Nodes represent common ancestors of two or more species.
• Leaves represent existing or extant species.