BIOSC-101 Lecture 16: Biosc-101_-_C16
9 Sep 2020
School
Department
Course
Professor
Biosc-101
Fundamentals of Biological Sciences
Class Notes
● Ecosystems
○ Food Chains and Food Webs
■ Trophic levels is any of the sequential stages in a food chain, occupied by
producers at the bottom and in turn by primary, secondary, and tertiary
consumers. Decomposers (detritivores) are sometimes considered to
occupy their own trophic level.
■ Photosynthetic producers such as plants are found in trophic level 1.
Organisms in level 1 do not consume other living organisms to obtain
nutrients.
■ Organisms in level 2 and beyond are called consumers because they
obtain food by eating plants or by eating organisms that have eaten plants.
● Consumers are identified as primary, secondary, and tertiary.
● Cows eat grass—primary
● People who eat meat from cattle—secondary
■ Energy pyramid is a diagram that shows the energy available at each
trophic level in an ecosystem.
■ Animals that feed on dead organic matter are called detritivores; some
specialize in eating dead animals (e.g. vultures) and others feed on dead
plant material (e.g., earthworms).
■ Bacteria and fungi that colonized dead material and absorb food molecules
from it are called decomposers.
○ Cycles of Matter
■ Biochemical cycles are the pathways that chemical elements follow
through ecosystems; they involve life (bio) and nonliving components
(geo).
○ Biochemical Cycles
■ The 3 cycles that are key for living things are the water cycle, carbon
cycle, and nitrogen cycle.
○ The Water Cycles
■ Solar energy powers the major processes driving Earth’s water cycle.
■ Water evaporates, condenses in the air, returns to Earth as precipitation,
and is transported through wind, river flow, and ocean currents
■ Land plants play an important role in the water cycle
■ They take up water through their roots and release it as vapor through tiny
holes in their leaves
■ This process, called transpiration, greatly accelerates the transfer of water
from soil to the atmosphere.
○ The Carbon Cycle
■ Carbon is cycle though a variety of biological and physical processes
■ Photosynthesis removes carbon dioxide from the atmosphere; aerobic
respiration by living plants and animals returns carbon to the air.
○ The Nitrogen Cycle
Document Summary
Trophic levels is any of the sequential stages in a food chain, occupied by producers at the bottom and in turn by primary, secondary, and tertiary consumers. Decomposers (detritivores) are sometimes considered to occupy their own trophic level. Photosynthetic producers such as plants are found in trophic level 1. Organisms in level 1 do not consume other living organisms to obtain nutrients. Organisms in level 2 and beyond are called consumers because they obtain food by eating plants or by eating organisms that have eaten plants. Consumers are identified as primary, secondary, and tertiary. Energy pyramid is a diagram that shows the energy available at each trophic level in an ecosystem. Animals that feed on dead organic matter are called detritivores; some specialize in eating dead animals (e. g. vultures) and others feed on dead plant material (e. g. , earthworms). Bacteria and fungi that colonized dead material and absorb food molecules from it are called decomposers.
