Lesson Notes By Weeks and Term - Senior Secondary 1

TERM – 2^ND TERM

WEEK FOUR

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Biology

Topic: FUNCTIONING ECOSYSTEM

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. Identify aspects of a functioning Ecosystem 
2. Describe the role of autotrophs, heterotrophs and decomposers

iii. Define trophic levels.

1. Differentiate between food chain and food web
2. Describe how energy flow along the trophic levels.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS:  Videos, loud speaker, textbook, picture

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION	TEACHER’S ACTIVITY	STUDENT’S ACTIVITY
STEP 1 INTRODUCTION	The teacher discusses the aspects of a functioning Ecosystem	Students pay attention
STEP 2 EXPLANATION	Teacher discusses the role of autotrophs, heterotrophs and decomposers	Students pay attention and participate
STEP 3 DEMONSTRATIO N	Teacher introduce trophic levels and  explains how energy flow along the trophic levels.	Students pay attention and participate
STEP 4 NOTE TAKING	The teacher writes a summarized note on the board	The students copy the note in their books

 

NOTE

FUNCTIONING ECOSYSTEM

A functioning ecosystem involves the interplay of various components and processes that collectively maintain balance and sustain life. The following are aspects of a functioning ecosystem include:

1. Biodiversity: A diverse array of species contributes to ecosystem stability. Each species plays a unique role, and interactions among them support ecological processes.
2. Energy Flow: Ecosystems rely on the flow of energy through food chains and webs. Producers (plants) capture sunlight, and energy is transferred through consumers (herbivores, carnivores) and decomposers.
3. Nutrient Cycling: Nutrients such as carbon, nitrogen, and phosphorus cycle through the ecosystem. Decomposers break down organic matter, returning nutrients to the soil for reuse by plants.
4. Abiotic Factors: Physical and chemical components, like climate, soil, and water, influence the ecosystem. These abiotic factors shape the distribution and behavior of organisms.
5. Water Cycle: Movement of water through precipitation, evaporation, and transpiration is essential for maintaining water availability in ecosystems.

Roles of Autotrophs, Heterotrophs and decomposers

Autotrophs, heterotrophs, and decomposers play crucial roles in ecological systems, collectively contributing to the flow of energy and cycling of nutrients:

1. Autotrophs (Producers): Autotrophs are organisms capable of synthesizing their own food using sunlight or inorganic compounds. Most commonly, plants perform photosynthesis, converting solar energy into chemical energy stored in organic compounds.

Autotrophs form the foundation of ecosystems by producing organic matter. They are essential for energy flow as they create the initial biomass that sustains all other trophic levels.

2. Heterotrophs (Consumers): Heterotrophs are organisms that obtain energy by consuming other organisms. They cannot produce their own food and depend on autotrophs or other heterotrophs for nutrients and energy. Heterotrophs are categorized into primary consumers (herbivores), secondary consumers (carnivores that feed on herbivores), and tertiary consumers (carnivores that feed on other carnivores).

Heterotrophs are vital for the transfer of energy through trophic levels. They participate in the consumption and recycling of organic matter.

3. Decomposers: Decomposers, primarily bacteria and fungi, break down organic matter into simpler compounds. They play a crucial role in the recycling of nutrients by decomposing dead organisms and organic waste.Decomposers secrete enzymes that break down complex organic molecules into simpler forms, releasing nutrients back into the environment.

Trophic level

A trophic level is a position in the food chain or web of an ecosystem, representing a group of organisms that share the same function in the transfer of energy and nutrients. There are typically three main trophic levels:

1. Primary Producers (Trophic Level 1): Primary producers, often autotrophs like plants, algae, and certain bacteria, are at the base of the food chain. They produce organic compounds through processes like photosynthesis, capturing energy from the sun or inorganic sources.
2. Consumers (Trophic Levels 2, 3, etc.):

   - Primary Consumers (Herbivores - Trophic Level 2): Herbivores feed directly on primary producers (plants) and represent the second trophic level.

   - Secondary Consumers (Carnivores - Trophic Level 3): Carnivores that feed on herbivores occupy the third trophic level.

   - Tertiary Consumers (Carnivores - Trophic Level 4): Predators that consume other carnivores are at the fourth trophic level.

3. Decomposers (Trophic Level Decomposer): Decomposers, such as bacteria and fungi, break down dead organic matter from all trophic levels. They play a vital role in nutrient recycling, releasing essential elements back into the environment.

Food chain and  food web.

A food chain is a linear sequence showing the flow of energy from one organism to another. For example, grass is eaten by a herbivore, which is then consumed by a carnivore. In contrast, a food web is a more complex, interconnected network of multiple food chains. It illustrates how different species in an ecosystem are linked through their feeding relationships, providing a more realistic representation of energy flow.

Energy Flow along trophic level (Pyramid of number energy and biomas).

In an ecosystem, energy flows through trophic levels, representing different positions in the food chain. The energy pyramid, pyramid of numbers, and pyramid of biomass illustrate this flow.

 

1. Energy Pyramid: Shows the flow of energy from one trophic level to the next. It also shows how energy is lost as heat during metabolic processes, so each higher level receives less energy.

 Typically, the primary producers (plants) form the broad base, with energy decreasing as you move up to consumers.

2. Pyramid of Numbers: Represents the number of organisms at each trophic level. It may not always follow a pyramid shape; it can be inverted or irregular based on the size and reproductive rates of organisms.

In some ecosystems, a large number of small organisms (e.g., insects) can support fewer consumers (e.g., predators).

3. Pyramid of Biomass: Illustrates the total biomass (weight) of organisms at each trophic level.

Biomass decreases as you move up the pyramid due to energy loss and the fact that higher trophic levels require more energy for maintenance. Like the energy pyramid, it generally has a pyramid shape.

EVALUATION: 1. identify 5 aspects of a functioning Ecosystem 

2. Discuss the roles of autotrophs, heterotrophs and decomposers
3. What are trophic level?
4. Describe how energy flow along the trophic levels

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively