# Lesson Notes By Weeks and Term - Senior Secondary 1

Population studies

TERM – 2ND TERM

WEEK THREE

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Biology

Topic:   POPULATION STUDIES

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

1. Define population size and population density
2. Identify the methods of studying population
3. Identify factors that affect population
4. List instruments for measuring ecological factors
5. Describe the relationship between soil types and water holding capacity

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 explains population studies using population size and population density Students pay attention STEP 2 EXPLANATION Teacher explains the methods of studying population and factors affecting population Students pay attention and participate STEP 3 DEMONSTRATIO N Teacher discusses relationship between soil types and water holding capacity 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

POPULATION STUDIES

Population Size:  This is the total number of individuals of a species in a defined area at a specific time. The population size can be estimated through direct counting, mark and recapture methods, or aerial surveys.

Population Density: This is the number of individuals of a species per unit area or volume. The population density is calculated by dividing the population size by the total area or volume of the habitat.

It provides insights into how closely individuals are packed in a given space, influencing resource availability and interactions.

Dominance: This is the degree to which a particular species or individual has a disproportionately large impact on its community, influencing the distribution and abundance of other species. Dominance is often assessed through species abundance and their impact on community structure. In plant communities, dominant species may occupy a large portion of the habitat and influence the composition of associated species.

Methods of Population Studies

1. Census: This is the bfirect counting of all individuals in a population. It provides an accurate count, although it's Impractical for large, mobile, or elusive populations.
2. Mark and Recapture: It is a subset of individuals is captured, marked, released, and later recaptured. The proportion of marked individuals in the second capture is used to estimate the total population size. It is effective for mobile or elusive populations.
3. Quadrat Sampling: Sampling units (quadrats) of known size are randomly placed in a habitat, and the number of individuals within each quadrat is counted. It is useful for immobile or sessile organisms, however, assumes homogeneity within quadrats, may not capture spatial variations.
4. Transect Sampling: Here a line or path is established through a habitat, and the number of individuals or species intersecting the line is recorded. It is useful for studying distribution along a gradient.
5. Remote Sensing: The use of satellite or aerial imagery to estimate population size or vegetation cover. It is useful for large-scale studies.

Factors Affecting Population

1. Birth Rate: The number of births per unit of population over a specified period.

High birth rates contribute to population growth, while low birth rates can lead to stabilization or decline.

1. Death Rate: The number of deaths per unit of population over a specified period. High death rates decrease population size, while low death rates support population growth.
2. Migration: The movement of individuals into (immigration) or out of (emigration) a population or geographic area. Immigration increases population size, while emigration decreases it. Migration can alter population composition.
3. Resource Availability: The availability of essential resources such as food, water, shelter, and space. However, limited resources can lead to competition, impacting population size and distribution.
4. Environmental Conditions: Factors like climate, weather, and habitat conditions.

The presence of harsh environmental conditions can limit population growth, while favorable conditions can support larger populations.

1. Disease and Parasitism:

- Disease: Pathogens that affect the health of individuals.

- Parasitism: Organisms living on or in another organism, benefiting at the host's expense.

Disease and parasitism can decrease population size by causing illness or death.

1. Natural Disasters: Catastrophic events like floods, wildfires, earthquakes, and hurricanes. Natural disasters can have significant impacts on population size and distribution.
2. Human Activities: Activities like Hunting and Fishing leads overharvesting of species for food or trade, while habitat Destruction leads to deforestation, urbanization, and pollution. All these human activities can cause population decline or endangerment.
3. Climate Change: Long-term changes in temperature, precipitation, and weather patterns. Climate change alters habitat suitability, affecting the distribution and abundance of populations.

Ecological Instrument and measurement of Ecological Factors

Ecological instruments are devices used to measure various environmental factors in ecosystems. Common instruments include:

1. Hydrometers and pH Meters: Measure water properties like acidity (pH) and specific gravity.
2. Anemometers: Gauge wind speed, crucial for understanding air circulation in an ecosystem.
3. Thermometers: Record temperature variations, influencing species distribution and behavior.
4. Barometers: Assess atmospheric pressure, providing insights into weather patterns.
5. Spectrophotometers: Analyze the absorption of light in water, aiding in water quality assessments.
6. Rain Gauges: Record precipitation levels, crucial for understanding water availability.

Relationship between soil types and the water-holding capacity

The relationship between soil types and the water-holding capacity of soil is influenced by several factors:

1. Texture: Soil texture, determined by the proportion of sand, silt, and clay, affects water retention. Clay soils have smaller particles and can hold more water than sandy soils.
2. Porosity: Soil porosity, the amount of pore space between soil particles, influences water-holding capacity. Well-structured soils with good porosity can retain more water.
3. Organic Matter: The presence of organic matter enhances soil structure and water retention. Organic matter acts like a sponge, holding water and making it available to plants.
4. Depth of Soil Profile: Deeper soil profiles generally have more space to store water, benefiting vegetation during dry periods.
5. Compaction: Compacted soils have reduced pore spaces, limiting water retention. Uncompacted soils allow for better water infiltration and storage.
6. Topography: Sloped areas may experience faster water runoff, reducing water availability for plants. Flat or gently sloping terrain allows for better water retention.

EVALUATION: 1. Differentiate between population size and population density

1. What is dominance
2. Identify 4 factors affecting population
3. Describe the relationship between soil types and water holding capacity.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively