Population Dynamics and Structures

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Questions and Answers

What is a cohort?

A group of individuals born at the same time and belonging to the same species and population. (correct)

A group of individuals with varying ages.

A group of individuals from different populations.

A group of individuals from different species.

What does the per capita birth rate (b) in a population represent?

The number of births per individual in the population. (correct)

The average time it takes for an individual to reproduce.

The number of deaths in the population during a specified period.

The change in population size over time.

In the logistics model of population growth, what does intraspecific competition refer to?

Competition between predators and prey.

Competition for limiting resources between individuals of the same species. (correct)

Competition between different populations.

Competition between individuals of different species.

If the per capita growth rate (r) in a population is greater than zero (r > 0), what does this indicate about the population's growth?

The population is growing. Signup and view all the answers

What are plants classified as in terms of cellular makeup?

Multicellular, photosynthetic eukaryotes Signup and view all the answers

How many living plant species does the Kingdom Plantae encompass?

At least 400,000 Signup and view all the answers

What is believed to be the most likely algal ancestor of land plants?

Charophyte algae Signup and view all the answers

Land plants evolved from freshwater green algae about 475 million years ago.

True Signup and view all the answers

The main adaptations of plants to land include protection against ______.

desiccation Signup and view all the answers

Which of the following are considered nonvascular plants?

Liverworts Signup and view all the answers

What is the primary function of stomata in plants?

Allow air to enter for gas exchange Signup and view all the answers

Which group of plants contains seed plants?

Spermatophyta Signup and view all the answers

Which adaptation helps prevent water loss in plants?

Cuticle Signup and view all the answers

Plants need a ______ environment for reproduction and dispersal.

dry Signup and view all the answers

Study Notes

Population Age Structure

Describes the relative number of individuals in each age class within a population
Important for understanding a population's growth potential and future trends

Survivorship

Age-specific survivorship represents the proportion of individuals alive at the beginning of an age interval that survive until the start of the next age interval.

Sex Ratio

Important for understanding potential population growth, especially focusing on females since they are the ones who give birth.

Population Growth

Increases in population size are primarily influenced by birth, death, immigration, and emigration.

Cohort

A group of individuals born at the same time and belonging to the same species and population

Survivorship Curves

Type III: Characterized by high juvenile mortality followed by low mortality once offspring reach a critical size.
- This type of survivorship is common for species that produce large numbers of offspring with little parental care.

Per Capita Birth Rate (b)

Represents the number of births per individual in the population.

Carrying Capacity (K)

The maximum population size that an environment can sustainably support, given the available resources.

Carrying Capacity and Logistic Model

The logistic model of population growth incorporates carrying capacity (K) and intraspecific competition.

Intraspecific Competition

Competition for limiting resources between individuals of the same species.
- This competition can limit population growth as individuals struggle for food, water, space, and other resources.

Per Capita Growth Rate (r)

If the per capita growth rate (r) is greater than zero (r > 0), it indicates that the population is growing.
- If r is less than zero (r < 0), the population is decreasing.
- If r is equal to zero (r = 0), the population is stable.

Plant Evolution and Diversity

Plants are multicellular, photosynthetic eukaryotes, with at least 400,000 living species, including approximately 24,000 in Southern Africa.
Plants evolved from freshwater green algae (chlorophyta) about 475 million years ago (mya).
The most likely algal ancestor of plants is charophyte algae.

Adaptations to Land

Protection Against Desiccation:
- Cuticle: A waxy outer layer that slows water loss and prevents drying out.
- Stomata: Tiny openings in epidermal surfaces that allow for gas exchange and prevent direct exposure of moist cell surfaces to the atmosphere. Stomata are formed by guard cells that can open and close the space between them.

Transition From Water to Land

Water Environment:
- Water is plentiful, making desiccation a non-issue.
- The plant body is supported by the water.
- Light availability can be limited.
- CO2 availability and diffusion is restricted.
Land Environment:
- Water is scarce, making desiccation a serious problem.
- The plant body lacks support from the surrounding environment.
- Light is readily available.
- CO2 is plentiful.

Major Plant Groups

Bryophytes (Nonvascular):
- Liverworts (Hepatophyta)
- Mosses (Bryophyta)
- Hornworts (Anthocerophyta)
- Features: Lack vascular tissues and lignin, rhizomes, gametophyte dominant, gas exchange via pores.
Seedless Vascular Plants:
- Club mosses (Lycophyta)
- Ferns, whisk ferns and horsetails (Monilophyta)
- Features: Swimming sperm, no seeds, heterospory and homospory.
Seed Plants (Spermatophyta):
- Gymnosperms
- Angiosperms
- Features: Nonswimming sperm in pollen, seeds, heterospory, vessel elements in angiosperms.
Tracheophyta (Vascular):
- Features: Apical meristem, stomata that open and close, lignin, tracheids, vascular tissues (xylem, phloem), root and shoot systems, sporophyte dominant.

Key Adaptations for Land Life

Protection from desiccation (drying out).
Mechanism for taking up water and minerals.
Mechanism for transporting water and minerals.
Support tissue to keep plants upright and expose photosynthetic surfaces.
Reproduction in a dry environment.
Effective dispersal without water.

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Description

This quiz delves into the critical components of population dynamics, including age structure, survivorship, and sex ratios. Understand how these factors influence a population’s growth potential and future trends. Explore concepts like cohort analysis and survivorship curves, focusing on the implications of these dynamics in ecology.