Los ecosistemas 1º ESO

Scientific concepts & nature phenomena presented

1) Ecosystems and Earth’s life-support systems

• Ecosystem concept: a community of living beings (biocenosis) living in a specific place (biotope), including:
  • relationships among organisms
  • relationships between organisms and their physical environment
• Human-modified ecosystem example: cultivated plants and paths created by humans.
• Why Earth supports life (interacting systems):
  • Hydrosphere: seas, oceans, rivers, glaciers; water is essential
  • Atmosphere: gases like oxygen and nitrogen; provides the greenhouse effect (average ~15°C) and protects from UV radiation
  • Geosphere: rocky part/ground
  • Biosphere: all living beings on Earth

2) Biodiversity depends on place and climate (habitats)

• Organisms live in specific locations determined largely by climate and adaptation.
• Examples:
  • polar penguins can’t tolerate heat
  • giraffes need appropriate food and conditions

3) Biocenosis and biotope (biotic vs. abiotic parts)

• Biocenosis (biotic part):
  • the set of all living organisms in an ecosystem
  • their relationships, such as nesting, feeding, schooling/herds
• Biotope (abiotic/inert part):
  • physical and chemical environment: rocks, soil, air, water
  • climatic parameters, including:
    • temperature
    • salinity
    • water depth
    • precipitation
    • minimum/maximum temperatures

4) Relationships among organisms (biotic interactions)

• Intraspecific relationships (same species):
  • example: gregarious associations (frocks/herds/schools)
  • benefits: protection and improved survival/feeding
• Interspecific relationships (different species):
  • Parasitism example:
    • prickly pear cactus weakened/killed by cochineal insect
    • the insect benefits; the host is harmed
  • Human analogies mentioned:
    • lice
    • intestinal worms

5) Trophic levels and matter/energy flow

• Major trophic groups in ecosystems:
  • Producers (autotrophs): mainly plants and algae, producing organic matter from inorganic matter using sun energy
  • Consumers (heterotrophs):
    • Primary consumers: herbivores that feed on producers
    • Secondary consumers: typically carnivores (can be omnivores) that feed on primary consumers
    • Tertiary consumers: feed on secondary consumers
  • Decomposers: mainly bacteria and fungi
    • recycle organic matter from dead organisms into inorganic matter for producers
• Food chains
  • Built by observing “who eats whom”
  • arrows show the direction of eating (toward the eater)
• Food webs
  • more realistic than food chains because one organism can be eaten by multiple species
• Matter vs. energy in ecosystems
  • Matter is recycled through trophic levels and decomposers
  • Energy is not recycled; it flows one direction: Sun → producers → consumers
  • energy loss occurs at each level; only about 10% is passed to the next trophic level (as stated)

6) Abiotic factors: terrestrial vs. aquatic

• Terrestrial abiotic factors

  • Temperature (varies by latitude, altitude, day/night, seasons)
  • Light intensity
  • Day length
  • Humidity (higher near seas/large water bodies)
  • Precipitation (amount and seasonal distribution)
  • use of climate graphs (monthly precipitation and temperature curves)

• Aquatic abiotic factors

  • Light and depth zones
    • Tropic zone: sunlight reaches
    • Rustic zone (as named in subtitles): sunlight insufficient for photosynthesis to continue normally (some organisms can still exist)
    • Aphotic zone: no sunlight; only heterotrophs can live there
    • example: seagrass (Posidonia) up to the light limit; below it, light no longer supports photosynthetic organisms
  • Pressure
    • increases with depth
    • deep animals may have flattened morphologies to withstand pressure
  • Salinity
    • e.g., Dead Sea salinity prevents many fish from living there
  • Oxygen
    • lower in water than in air; decreases with depth
    • currents can transport oxygen downward, allowing animal survival even without photosynthetic organisms
  • Water temperature
    • influenced by sunlight near the surface
    • around 300 m deeper, temperature becomes relatively stable (~2°C), not below 0°C

7) Major terrestrial ecosystems/biomes by climate (overview)

• Mentioned terrestrial biomes (with examples):
  • Polar desert and taiga
  • Temperate zones: deciduous forests, Mediterranean forest, steppe
  • Warm zones: hot deserts, savanna
• Note: subtitles indicate a slide/PPT breakdown by climatic zones.

8) Ecosystem examples of regions and types

• Aquatic ecosystem examples: birds, reeds, algae, crab, insects
• High mountain area example (possibly Picos de Europa):
  • nest-building and presence of multiple organism groups (bacteria/fungi/plants/animals mentioned broadly)

Researchers or sources featured

No specific researchers, scientists, or external sources are named in the subtitles.